WorldWideScience

Sample records for wave energy point

  1. A Design Outline for Floating Point Absorber Wave Energy Converters

    Directory of Open Access Journals (Sweden)

    Mohammed Faizal

    2014-04-01

    Full Text Available An overview of the most important development stages of floating point absorber wave energy converters is presented. At a given location, the wave energy resource has to be first assessed for varying seasons. The mechanisms used to convert wave energy to usable energy vary for different wave energy conversion systems. The power output of the generator will have variations due to varying incident waves. The wave structure-interaction leads to modifications in the incident waves; thus, the power output is also affected. The device has to be stable enough to prevent itself from capsizing. The point absorber will give optimum performance when the incident wave frequencies correspond to the natural frequency of the device. The methods for calculating natural frequencies for pitching and heaving systems are presented. Mooring systems maintain the point absorber at the desired location. Various mooring configurations as well as the most commonly used materials for mooring lines are discussed. An overview of scaled modelling is also presented.

  2. Numerical Modeling of a Wave Energy Point Absorber

    DEFF Research Database (Denmark)

    Hernandez, Lorenzo Banos; Frigaard, Peter; Kirkegaard, Poul Henning

    2009-01-01

    The present study deals with numerical modelling of the Wave Star Energy WSE device. Hereby, linear potential theory is applied via a BEM code on the wave hydrodynamics exciting the floaters. Time and frequency domain solutions of the floater response are determined for regular and irregular seas....... Furthermore, these results are used to estimate the power and the energy absorbed by a single oscillating floater. Finally, a latching control strategy is analysed in open-loop configuration for energy maximization....

  3. Optimal Control Of Nonlinear Wave Energy Point Converters

    DEFF Research Database (Denmark)

    Nielsen, Søren R.K.; Zhou, Qiang; Kramer, Morten

    2013-01-01

    In this paper the optimal control law for a single nonlinear point absorber in irregular sea-states is derived, and proven to be a closed-loop controller with feedback from measured displacement, velocity and acceleration of the floater. However, a non-causal integral control component dependent...... idea behind the control strategy is to enforce the stationary velocity response of the absorber into phase with the wave excitation force at any time. The controller is optimal under monochromatic wave excitation. It is demonstrated that the devised causal controller, in plane irregular sea states......, absorbs almost the same power as the optimal controller....

  4. Discretized energy minimization in a wave guide with point sources

    Science.gov (United States)

    Propst, G.

    1994-01-01

    An anti-noise problem on a finite time interval is solved by minimization of a quadratic functional on the Hilbert space of square integrable controls. To this end, the one-dimensional wave equation with point sources and pointwise reflecting boundary conditions is decomposed into a system for the two propagating components of waves. Wellposedness of this system is proved for a class of data that includes piecewise linear initial conditions and piecewise constant forcing functions. It is shown that for such data the optimal piecewise constant control is the solution of a sparse linear system. Methods for its computational treatment are presented as well as examples of their applicability. The convergence of discrete approximations to the general optimization problem is demonstrated by finite element methods.

  5. Performance of a Tethered Point Wave-Energy Absorber in Regular and Irregular Waves

    KAUST Repository

    Bachynski, Erin E.

    2010-01-01

    The importance of the mooring system on the dynamic response of a point-absorber type ocean-wave energy converter (WEC) is investigated using a frequency-domain approach. In order to ensure the safety of WECs, careful consideration of the response and resonance frequencies in all motions must be evaluated, including the effects of the mooring system. In this study, a WEC floater with a closed, flat bottom is modeled as a rigid vertical cylinder tethered by elastic mooring lines. The WEC hydrodynamic added mass and damping are obtained using established potential-flow methods, with additional damping provided by the energy-extraction system. The results show that the response of the WEC, and the corresponding power takeoff, varies with the diameter-to-draft (D=T) ratio, mooring system stiffness, and mass distribution. For a given wave climate in Northern California, near San Francisco, the heave energy extraction is found to be best for a shallow WEC with a soft mooring system, compared to other systems that were examined. This result assumes a physical limit (cap) on the motion which is related to the significant wave height to draft ratio. Shallow draft designs, however, may experience excessive pitch motions and relatively larger viscous damping. In order to mitigate the pitch response, the pitch radius of gyration should be small and the center of mass should be low. Copyright © 2010 by ASME.

  6. Optimal Discrete PTO Force Point Absorber Wave Energy Converters in Regular Waves

    DEFF Research Database (Denmark)

    Hansen, Anders Hedegaard; Pedersen, Henrik C.

    2013-01-01

    the conventional fluid power systems suffer of poor efficiency. Therefore discrete fluid power force systems have been proposed. Limited research has, however, been conducted with focus on choosing the discrete force levels and force profiles for a discrete PTO system for WECs. This paper is to support the design...... of discrete force systems for PTO, by focusing on how to choose the optimal PTO force levels and force profile when seeking to increase energy harvesting. The work concerns point absorber WECs and utilises a simple float model based on linear wave theory. Utilising the principle of superposition...

  7. Experiments with Point Absorber Type Wave Energy Converters in a Large-Scale Wave Basin

    DEFF Research Database (Denmark)

    Stratigaki, Vasiliki; Troch, Peter; Stallard, Tim

    2014-01-01

    Wave Energy Converters (WECs) extract energy from ocean waves and have the potential to produce a significant contribution of electricity from renewable sources. However, large "WEC farms" or "WEC arrays" are expected to have "WEC array effects", expressed as the impact of the WECs on the wave...... of geometric layout configurations and wave conditions. WEC response, wave induced forces on the WECs and wave field modifications have been measured. Each WEC consists of a buoy with diameter of 0.315 m. Power take-off is modeled by realizing friction based energy dissipation through damping of the WECs...... array effects and for validation and extension of numerical models. This model validation will enable optimization of the geometrical layout of WEC arrays for real applications and reduction of the cost of energy from wave energy systems....

  8. Bottom Slamming on Heaving Point Absorber Wave Energy Devices

    DEFF Research Database (Denmark)

    De Backer, Griet; Vantorre, Marc; Frigaard, Peter;

    2010-01-01

    Oscillating point absorber buoys may rise out of the water and be subjected to bottom slamming upon re-entering the water. Numerical simulations are performed to estimate the power absorption, the impact velocities and the corresponding slamming forces for various slamming constraints. Three buoy...

  9. Synthesis of Numerical Methods for Modeling Wave Energy Converter-Point Absorbers: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.; Yu, Y. H.

    2012-05-01

    During the past few decades, wave energy has received significant attention among all ocean energy formats. Industry has proposed hundreds of prototypes such as an oscillating water column, a point absorber, an overtopping system, and a bottom-hinged system. In particular, many researchers have focused on modeling the floating-point absorber as the technology to extract wave energy. Several modeling methods have been used such as the analytical method, the boundary-integral equation method, the Navier-Stokes equations method, and the empirical method. However, no standardized method has been decided. To assist the development of wave energy conversion technologies, this report reviews the methods for modeling the floating-point absorber.

  10. Energy of hydrodynamic and magnetohydrodynamic waves with point and continuous spectra

    Science.gov (United States)

    Hirota, M.; Fukumoto, Y.

    2008-08-01

    Energy of waves (or eigenmodes) in an ideal fluid and plasma is formulated in the noncanonical Hamiltonian context. By imposing the kinematical constraint on perturbations, the linearized Hamiltonian equation provides a formal definition of wave energy not only for eigenmodes corresponding to point spectra but also for singular ones corresponding to a continuous spectrum. The latter becomes dominant when mean fields have inhomogeneity originating from shear or gradient of the fields. The energy of each wave is represented by the eigenfrequency multiplied by the wave action, which is nothing but the action variable and, moreover, is associated with a derivative of a suitably defined dispersion relation. The sign of the action variable is crucial to the occurrence of Hopf bifurcation in Hamiltonian systems of finite degrees of freedom [M. G. Krein, Dokl. Akad. Nauk SSSR, Ser. A 73, 445 (1950)]. Krein's idea is extended to the case of coalescence between point and continuous spectra.

  11. Experimental Wave Tank Test for Reference Model 3 Floating-Point Absorber Wave Energy Converter Project

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Y. H. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Lawson, M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Li, Y. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Previsic, M. [Re Vision Consulting, Sacramento, CA (United States); Epler, J. [Re Vision Consulting, Sacramento, CA (United States); Lou, J. [Oregon State Univ., Corvallis, OR (United States)

    2015-01-01

    The U.S. Department of Energy established a reference model project to benchmark a set of marine and hydrokinetic technologies including current (tidal, open-ocean, and river) turbines and wave energy converters. The objectives of the project were to first evaluate the status of these technologies and their readiness for commercial applications. Second, to evaluate the potential cost of energy and identify cost-reduction pathways and areas where additional research could be best applied to accelerate technology development to market readiness.

  12. Gyroscopic power take-off wave energy point absorber in irregular sea states

    DEFF Research Database (Denmark)

    Zhang, Zili; Chen, Bei; Nielsen, Søren R.K.

    2017-01-01

    Highlights •A GyroPTO wave energy point absorber with magnetic coupling mechanism is proposed. •A 4DOF nonlinear model of the GyroPTO absorber has been derived. •Rational approximations are performed on the radiation damping moments. •Synchronization of the device is more easily maintained in nar...... in narrow-banded sea waves. •The generator gain and the magnetic coupling constant influence the performance of the device....

  13. Stability analysis of the Gyroscopic Power Take-Off wave energy point absorber

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.; Zhang, Zili; Kramer, Morten Mejlhede

    2015-01-01

    The Gyroscopic Power Take-Off (GyroPTO) wave energy point absorber consists of a float rigidly connected to a lever. The operational principle is somewhat similar to that of the so-called gyroscopic hand wrist exercisers, where the rotation of the float is brought forward by the rotational partic...

  14. Numerical modelling of wave energy absorption by a floating point absorber system

    Energy Technology Data Exchange (ETDEWEB)

    Backer, G. De; Banasiak, R.; Beels, C. [Ghent University Civil Engineering Department, Zwijnaarde (Belgium); J. De Rouck, J. De

    2007-07-01

    Point absorbers are wave energy converters (WECs) consisting of small (floating) bodies oscillating with either one or more degrees of freedom. They can either move with respect to a fixed reference, or with respect to a floating reference. Different buoy geometries are evaluated to obtain the ideal values of size, shape and draft with regard to power absorption for a given moderate wave climate. In this paper, the performance of a heaving point absorber in a floating platform is analysed in a linear way.

  15. Observations of High-frequency Internal Wave Energy Offshore of Point Loma, California

    Science.gov (United States)

    Rhee, K.; Crosby, S. C.; Fiedler, J. W.

    2016-12-01

    As coastally directed internal wave energy shoals in shallow water, the resulting bores can transport cold, dense, nutrient-rich waters shoreward, influencing local fauna and ultimately dissipating tidal energy into heat. Understanding the mechanisms, propagation, and resultant transport is crucial for determining the physical-biological interactions along our coasts. We observed significant internal wave energy offshore of Point Loma, San Diego using a thermistor chain moored in 22m depth. Temperature observations spaced 1.5m apart from 0 to 18m were sampled at 2Hz and recorded for a period of ten days during July 2016. Temperature, salinity, oxygen, and nutrient profiles were obtained at 3 stations further offshore during deployment and recovery cruises. At the time of mooring deployment, thermocline depth was 10 to 20m. During recovery we observed a significant decrease of thermocline depth, which was likely caused by surface mixing during a strong wind event. During the 10-day deployment we observed many high frequency (5 to 10 minute periods) internal waves events. In addition, we noticed rapid temperature changes (4oC in less than a minute) suggestive of internal bores; however, other events appeared to be linear, possibly indicating unbroken internal waves. Here, we examine the critical slope for linear mode-1 propagation, the correlation of these events with tidal ebb and flow, and infer how a deeper mixed layer effects internal wave propagation.

  16. Constrained Optimal Stochastic Control of Non-Linear Wave Energy Point Absorbers

    DEFF Research Database (Denmark)

    Sichani, Mahdi Teimouri; Chen, Jian-Bing; Kramer, Morten

    2014-01-01

    The paper deals with the stochastic optimal control of a wave energy point absorber with strong nonlinear buoyancy forces using the reactive force from the electric generator on the absorber as control force. The considered point absorber has only one degree of freedom, heave motion, which is used...... presented in the paper. The effect of nonlinear buoyancy force – in comparison to linear buoyancy force – and constraints of the controller on the power outtake of the device have been studied in details and supported by numerical simulations....

  17. Experimental Investigation of the Power Generation Performance of Floating-Point Absorber Wave Energy Systems: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.; Yu, Y.; Epler, J.; Previsic, M.

    2012-04-01

    The extraction of energy from ocean waves has gained interest in recent years. The floating-point absorber (FPA) is one of the most promising devices among a wide variety of wave energy conversion technologies. Early theoretical studies mainly focused on understanding the hydrodynamics of the system and on predicting the maximum power that could be extracted by a heaving body. These studies evolve from the investigation of floating-body interactions in offshore engineering and naval architecture disciplines. To our best knowledge, no systematic study has been reported about the investigation of the power generation performance of an FPA with a close-to-commercial design. A series of experimental tests was conducted to investigate the power extraction performance of an FPA system.

  18. Numerical Time Integration Methods for a Point Absorber Wave Energy Converter

    DEFF Research Database (Denmark)

    Zurkinden, Andrew Stephen; Kramer, Morten

    2012-01-01

    The objective of this abstract is to provide a review of models for motion simulation of marine structures with a special emphasis on wave energy converters. The time-domain model is applied to a point absorber system working in pitch mode only. The device is similar to the well-known Wavestar...... float located in the Danish North Sea. The main objective is to produce a tool that can accurately simulate the dynamics of a floating structure with an arbitrary geometry provided the frequency domain coefficients are calculated beforehand. The latter calculation is based on linear fluid structure...... interaction (small deformations of the fluid surface and body), inviscid incompressible, irrotational flow and a linearized Euler-Bernoulli formulation of the fluid pressure. The time-domain analysis of a floating structure involves the calculation of a convolution integral between the impulse response...

  19. Semiclassical wave packet treatment of scattering resonances: application to the delta zero-point energy effect in recombination reactions.

    Science.gov (United States)

    Vetoshkin, Evgeny; Babikov, Dmitri

    2007-09-28

    For the first time Feshbach-type resonances important in recombination reactions are characterized using the semiclassical wave packet method. This approximation allows us to determine the energies, lifetimes, and wave functions of the resonances and also to observe a very interesting correlation between them. Most important is that this approach permits description of a quantum delta-zero-point energy effect in recombination reactions and reproduces the anomalous rates of ozone formation.

  20. Power maximization of a point absorber wave energy converter using improved model predictive control

    Science.gov (United States)

    Milani, Farideh; Moghaddam, Reihaneh Kardehi

    2017-08-01

    This paper considers controlling and maximizing the absorbed power of wave energy converters for irregular waves. With respect to physical constraints of the system, a model predictive control is applied. Irregular waves' behavior is predicted by Kalman filter method. Owing to the great influence of controller parameters on the absorbed power, these parameters are optimized by imperialist competitive algorithm. The results illustrate the method's efficiency in maximizing the extracted power in the presence of unknown excitation force which should be predicted by Kalman filter.

  1. Nearshore Tests of the Tidal Compensation System for Point-Absorbing Wave Energy Converters

    Directory of Open Access Journals (Sweden)

    Valeria Castellucci

    2015-04-01

    Full Text Available The power production of the linear generator wave energy converter developed at Uppsala University is affected by variations of mean sea level. The reason is that these variations change the distance between the point absorber located on the surface and the linear generator located on the seabed. This shifts the average position of the translator with respect to the center of the stator, thereby reducing the generator output power. A device mounted on the point absorber that compensates for tides of small range by regulating the length of the connection line between the buoy at the surface and the linear generator has been constructed and tested. This paper describes the electro-mechanical, measurement, communication and control systems installed on the buoy and shows the results obtained before its connection to the generator. The adjustment of the line was achieved through a linear actuator, which shortens the line during low tides and vice versa. The motor that drives the mechanical device was activated remotely via SMS. The measurement system that was mounted on the buoy consisted of current and voltage sensors, accelerometers, strain gauges and inductive and laser sensors. The data collected were transferred via Internet to a Dropbox server. As described within the paper, after the calibration of the sensors, the buoy was assembled and tested in the waters of Lysekil harbor, a few kilometers from the Uppsala University research site. Moreover, the performance of the sensors, the motion of the mechanical device, the power consumption, the current control strategy and the communication system are discussed.

  2. Universal breaking point asymptotic for energy spectrum of Riemann waves in weakly nonlinear non-dispersive media

    CERN Document Server

    Kartashova, Elena

    2013-01-01

    In this Letter we study the form of the energy spectrum of Riemann waves in weakly nonlinear non-dispersive media. For quadratic and cubic nonlinearity we demonstrate that the deformation of an Riemann wave over time yields an exponential energy spectrum which turns into power law asymptotic with the slope being approximately -8/3 at the last stage of evolution before breaking. We argue, that this is the universal asymptotic behaviour of Riemann waves in any nonlinear non-dispersive medium at the point of breaking. The results reported in this Letter can be used in various non-dispersive media, e.g. magneto-hydro dynamics, physical oceanography, nonlinear acoustics.

  3. Reflectors to Focus Wave Energy

    DEFF Research Database (Denmark)

    Kramer, Morten; Frigaard, Peter

    2005-01-01

    Wave Energy Converters (WEC’s) extract wave energy from a limited area, often a single point or line even though the wave energy is generally spread out along the wave crest. By the use of wave reflectors (reflecting walls) the wave energy is effectively focused and increased by approximately 30......-50%. Clearly longer wave reflectors will focus more wave energy than shorter wave reflectors. Thus the draw back is the increased wave forces for the longer wave reflectors. In the paper a procedure for calculating the energy efficiency and the wave forces on the reflectors are described, this by use of a 3D...... boundary element method. The calculations are verified by laboratory experiments and a very good agreement is found. The paper gives estimates of possible power benefit for different wave reflector geometries and optimal geometrical design parameters are specified. On this basis inventors of WEC’s can...

  4. Method and basis set dependence of anharmonic ground state nuclear wave functions and zero-point energies: application to SSSH.

    Science.gov (United States)

    Kolmann, Stephen J; Jordan, Meredith J T

    2010-02-07

    One of the largest remaining errors in thermochemical calculations is the determination of the zero-point energy (ZPE). The fully coupled, anharmonic ZPE and ground state nuclear wave function of the SSSH radical are calculated using quantum diffusion Monte Carlo on interpolated potential energy surfaces (PESs) constructed using a variety of method and basis set combinations. The ZPE of SSSH, which is approximately 29 kJ mol(-1) at the CCSD(T)/6-31G* level of theory, has a 4 kJ mol(-1) dependence on the treatment of electron correlation. The anharmonic ZPEs are consistently 0.3 kJ mol(-1) lower in energy than the harmonic ZPEs calculated at the Hartree-Fock and MP2 levels of theory, and 0.7 kJ mol(-1) lower in energy at the CCSD(T)/6-31G* level of theory. Ideally, for sub-kJ mol(-1) thermochemical accuracy, ZPEs should be calculated using correlated methods with as big a basis set as practicable. The ground state nuclear wave function of SSSH also has significant method and basis set dependence. The analysis of the nuclear wave function indicates that SSSH is localized to a single symmetry equivalent global minimum, despite having sufficient ZPE to be delocalized over both minima. As part of this work, modifications to the interpolated PES construction scheme of Collins and co-workers are presented.

  5. Efficient Wave Energy Amplification with Wave Reflectors

    DEFF Research Database (Denmark)

    Kramer, Morten Mejlhede; Frigaard, Peter Bak

    2002-01-01

    Wave Energy Converters (WEC's) extract wave energy from a limited area, often a single point or line even though the wave energy is generally spread out along the wave crest. By the use of wave reflectors (reflecting walls) the wave energy is effectively focused and increased to approximately 130......-140%. In the paper a procedure for calculating the efficiency and optimizing the geometry of wave reflectors are described, this by use of a 3D boundary element method. The calculations are verified by laboratory experiments and a very good agreement is found. The paper gives estimates of possible power benifit...... for different geometries of the wave reflectors and optimal geometrical design parameters are specified. On this basis inventors of WEC's can evaluate whether a specific WEC possible could benefit from wave reflectors....

  6. Characterization of loads on a hemispherical point absorber wave energy converter

    DEFF Research Database (Denmark)

    Jakobsen, Morten Møller; Beatty, Scott; Iglesias, G.

    2016-01-01

    Highlights •Slammingpressure on shell surface of hemisphere and comparison asymptotic theory. •Excitationforces from experiments and comparison with numerical inviscid boundary elementmodel. •Applicationof found coefficients in normal operation conditions for the wave energydevice.......Highlights •Slammingpressure on shell surface of hemisphere and comparison asymptotic theory. •Excitationforces from experiments and comparison with numerical inviscid boundary elementmodel. •Applicationof found coefficients in normal operation conditions for the wave energydevice....

  7. RF waves - Measuring their energy (dBm) in three points into Baia Mare, Romania

    Science.gov (United States)

    Pop-Vǎdean, A.; Pop, P. P.; Barz, C.; Lung, C.

    2016-02-01

    For the general public - and even for people with a science education - knowing to be subject to Radio Frequency (RF) radiation may arouse a feeling of uneasiness or even fear. Those feelings are instigated by the fact that you cannot see, hear, smell or feel RF radiation. Furthermore, the term „radiation” in itself has become very sensitive from the moment that the hazardous health effects of excessive radioactive decay (ionizing radiation) have become apparent. Media announcements of mostly unconfirmed scientific studies add to the feeling of uneasiness. So, naturally, whenever a new Global System of Mobile communications (GSM) base station is installed in an urban environment, the people living in the neighborhood may get worried. The same applies when we propose to use RF radiation for powering wireless sensors in office and home spaces using harvesting energy sistem (HE).In this paper we determine if the electromagnetic field intensity values, measured at certain points, respect the limits set by law, the protection against risks to human health.

  8. The Wave Energy Sector

    DEFF Research Database (Denmark)

    2017-01-01

    This Handbook for Ocean Wave Energy aims at providing a guide into the field of ocean wave energy utilization. The handbook offers a concise yet comprehensive overview of the main aspects and disciplines involved in the development of wave energy converters (WECs). The idea for the book has been ...

  9. The Wave Energy Sector

    DEFF Research Database (Denmark)

    2017-01-01

    This Handbook for Ocean Wave Energy aims at providing a guide into the field of ocean wave energy utilization. The handbook offers a concise yet comprehensive overview of the main aspects and disciplines involved in the development of wave energy converters (WECs). The idea for the book has been...... shaped by the development, research, and teaching that we have carried out at the Wave Energy Research Group at Aalborg University over the past decades. It is our belief and experience that it would be useful writing and compiling such a handbook in order to enhance the understanding of the sector...

  10. Near Shore Wave Modeling and applications to wave energy estimation

    Science.gov (United States)

    Zodiatis, G.; Galanis, G.; Hayes, D.; Nikolaidis, A.; Kalogeri, C.; Adam, A.; Kallos, G.; Georgiou, G.

    2012-04-01

    The estimation of the wave energy potential at the European coastline is receiving increased attention the last years as a result of the adaptation of novel policies in the energy market, the concernsfor global warming and the nuclear energy security problems. Within this framework, numerical wave modeling systems keep a primary role in the accurate description of wave climate and microclimate that is a prerequisite for any wave energy assessment study. In the present work two of the most popular wave models are used for the estimation of the wave parameters at the coastline of Cyprus: The latest parallel version of the wave model WAM (ECMWF version), which employs new parameterization of shallow water effects, and the SWAN model, classically used for near shore wave simulations. The results obtained from the wave models near shores are studied by an energy estimation point of view: The wave parameters that mainly affect the energy temporal and spatial distribution, that is the significant wave height and the mean wave period, are statistically analyzed,focusing onpossible different aspects captured by the two models. Moreover, the wave spectrum distribution prevailing in different areas are discussed contributing, in this way, to the wave energy assessmentin the area. This work is a part of two European projects focusing on the estimation of the wave energy distribution around Europe: The MARINA platform (http://www.marina-platform.info/ index.aspx) and the Ewave (http://www.oceanography.ucy.ac.cy/ewave/) projects.

  11. The Wave Energy Device

    DEFF Research Database (Denmark)

    Frigaard, Peter; Kofoed, Jens Peter; Tedd, James William

    2006-01-01

    The Wave Dragon is a 4 to 11 MW offshore wave energy converter of the overtopping type. It basically consists of two wave reflectors focusing the waves towards a ramp, a reservoir for collecting the overtopping water and a number of hydro turbines for converting the pressure head into power......'s first offshore wave energy converter. During this period an extensive measuring program has established the background for optimal design of the structure and regulation of the power take off system. Planning for full scale deployment of a 7 MW unit within the next 2 years is in progress. The prototype....... In the period from 1998 to 2001 extensive testing on a scale 1:50 model was carried at Aalborg University. During the last two years, testing has started on a prototype of the Wave Dragon in Nissum Bredning, Denmark (scale 1:4.5 of the North Sea). The prototype was grid connected in May 2003 as the world...

  12. Cycloidal Wave Energy Converter

    Energy Technology Data Exchange (ETDEWEB)

    Stefan G. Siegel, Ph.D.

    2012-11-30

    This program allowed further advancing the development of a novel type of wave energy converter, a Cycloidal Wave Energy Converter or CycWEC. A CycWEC consists of one or more hydrofoils rotating around a central shaft, and operates fully submerged beneath the water surface. It operates under feedback control sensing the incoming waves, and converts wave power to shaft power directly without any intermediate power take off system. Previous research consisting of numerical simulations and two dimensional small 1:300 scale wave flume experiments had indicated wave cancellation efficiencies beyond 95%. The present work was centered on construction and testing of a 1:10 scale model and conducting two testing campaigns in a three dimensional wave basin. These experiments allowed for the first time for direct measurement of electrical power generated as well as the interaction of the CycWEC in a three dimensional environment. The Atargis team successfully conducted two testing campaigns at the Texas A&M Offshore Technology Research Center and was able to demonstrate electricity generation. In addition, three dimensional wave diffraction results show the ability to achieve wave focusing, thus increasing the amount of wave power that can be extracted beyond what was expected from earlier two dimensional investigations. Numerical results showed wave cancellation efficiencies for irregular waves to be on par with results for regular waves over a wide range of wave lengths. Using the results from previous simulations and experiments a full scale prototype was designed and its performance in a North Atlantic wave climate of average 30kW/m of wave crest was estimated. A full scale WEC with a blade span of 150m will deliver a design power of 5MW at an estimated levelized cost of energy (LCOE) in the range of 10-17 US cents per kWh. Based on the new results achieved in the 1:10 scale experiments these estimates appear conservative and the likely performance at full scale will

  13. Tsunami wave energy

    CERN Document Server

    Dutykh, Denys

    2008-01-01

    In the vast literature on tsunami research, few articles have been devoted to energy issues. A theoretical investigation on the energy of waves generated by bottom motion is performed here. We start with the full incompressible Euler equations in the presence of a free surface and derive both dispersive and non-dispersive shallow-water equations with an energy equation. It is shown that dispersive effects only appear at higher order in the energy budget. Then we solve the Cauchy-Poisson problem of tsunami generation for the linearized water wave equations. Exchanges between potential and kinetic energies are clearly revealed.

  14. Ocean wave energy conversion

    CERN Document Server

    McCormick, Michael E

    2007-01-01

    This volume will prove of vital interest to those studying the use of renewable resources. Scientists, engineers, and inventors will find it a valuable review of ocean wave mechanics as well as an introduction to wave energy conversion. It presents physical and mathematical descriptions of the nine generic wave energy conversion techniques, along with their uses and performance characteristics.Author Michael E. McCormick is the Corbin A. McNeill Professor of Naval Engineering at the U.S. Naval Academy. In addition to his timely and significant coverage of possible environmental effects associa

  15. Electromagnetic wave energy converter

    Science.gov (United States)

    Bailey, R. L. (Inventor)

    1973-01-01

    Electromagnetic wave energy is converted into electric power with an array of mutually insulated electromagnetic wave absorber elements each responsive to an electric field component of the wave as it impinges thereon. Each element includes a portion tapered in the direction of wave propagation to provide a relatively wideband response spectrum. Each element includes an output for deriving a voltage replica of the electric field variations intercepted by it. Adjacent elements are positioned relative to each other so that an electric field subsists between adjacent elements in response to the impinging wave. The electric field results in a voltage difference between adjacent elements that is fed to a rectifier to derive dc output power.

  16. SSG Wave Energy Converter

    DEFF Research Database (Denmark)

    Margheritini, Lucia; Vicinanza, Diego; Frigaard, Peter

    2008-01-01

    head hydroturbines are converting the potential energy of the stored water into power. A key to success for the SSG will be the low cost of the structure and its robustness. The construction of the pilot plant is scheduled and this paper aims to describe the concept of the SSG wave energy converter...... and the studies behind the process that leads to its construction. The pilot plant is an on-shore full scale module in 3 levels with an expected power production of 320 MWh/y in the North Sea. Location, wave climate and laboratory tests results will be used here to describe the pilot plant and its characteristics.......The SSG (Sea Slot-cone Generator) is a wave energy converter of the overtopping type. The structure consists of a number of reservoirs one on the top of each others above the mean water level, in which the water of incoming waves is stored temporary. In each reservoir, expressively designed low...

  17. Wave directional spreading from point field measurements

    Science.gov (United States)

    McAllister, M. L.; Venugopal, V.; Borthwick, A. G. L.

    2017-04-01

    Ocean waves have multidirectional components. Most wave measurements are taken at a single point, and so fail to capture information about the relative directions of the wave components directly. Conventional means of directional estimation require a minimum of three concurrent time series of measurements at different spatial locations in order to derive information on local directional wave spreading. Here, the relationship between wave nonlinearity and directionality is utilized to estimate local spreading without the need for multiple concurrent measurements, following Adcock & Taylor (Adcock & Taylor 2009 Proc. R. Soc. A 465, 3361-3381. (doi:10.1098/rspa.2009.0031)), with the assumption that directional spreading is frequency independent. The method is applied to measurements recorded at the North Alwyn platform in the northern North Sea, and the results compared against estimates of wave spreading by conventional measurement methods and hindcast data. Records containing freak waves were excluded. It is found that the method provides accurate estimates of wave spreading over a range of conditions experienced at North Alwyn, despite the noisy chaotic signals that characterize such ocean wave data. The results provide further confirmation that Adcock and Taylor's method is applicable to metocean data and has considerable future promise as a technique to recover estimates of wave spreading from single point wave measurement devices.

  18. Denmark's clean energy future from waves

    Energy Technology Data Exchange (ETDEWEB)

    Lund, G. [Nova Pro, CADDET Danish National Team, Toelloese (Denmark)

    1999-10-01

    This article presents a brief overview of Denmark's wave energy programme which aims to develop wave energy plants to supply 15% of Denmark's energy consumption. Details are given of the Wave Dragon deep water floating wave power plant, the Swan DK3 backward bend duct buoy, the point absorber float, and the WavePlane floating device. The step by step development approach for projects accepted by the wave energy programme, and future options are discussed. (UK)

  19. Energy Wave Model of Atom

    Institute of Scientific and Technical Information of China (English)

    伍细如

    2015-01-01

    proton emits energy wave, electron could sits any position away from nucleus, but be the most stable just when it sits at the trough of energy wave, and this position accords with Bohr radius and Schr?dinger equation.

  20. Independent waves in complex source point theory.

    Science.gov (United States)

    Seshadri, S R

    2007-11-01

    The full-wave generalization of the scalar Gaussian paraxial beam is determined by an analytical continuation of the field of a point source for the Helmholtz equation. The regions of validity of the analytically continued fields are investigated for the outgoing and the incoming waves. The two independent wave functions valid for the two half-spaces separating the secondary source plane are deduced.

  1. Key features of wave energy.

    Science.gov (United States)

    Rainey, R C T

    2012-01-28

    For a weak point source or dipole, or a small body operating as either, we show that the power from a wave energy converter (WEC) is the product of the particle velocity in the waves, and the wave force (suitably defined). There is a thus a strong analogy with a wind or tidal turbine, where the power is the product of the fluid velocity through the turbine, and the force on it. As a first approximation, the cost of a structure is controlled by the force it has to carry, which governs its strength, and the distance it has to be carried, which governs its size. Thus, WECs are at a disadvantage compared with wind and tidal turbines because the fluid velocities are lower, and hence the forces are higher. On the other hand, the distances involved are lower. As with turbines, the implication is also that a WEC must make the most of its force-carrying ability-ideally, to carry its maximum force all the time, the '100% sweating WEC'. It must be able to limit the wave force on it in larger waves, ultimately becoming near-transparent to them in the survival condition-just like a turbine in extreme conditions, which can stop and feather its blades. A turbine of any force rating can achieve its maximum force in low wind speeds, if its diameter is sufficiently large. This is not possible with a simple monopole or dipole WEC, however, because of the 'nλ/2π' capture width limits. To achieve reasonable 'sweating' in typical wave climates, the force is limited to about 1 MN for a monopole device, or 2 MN for a dipole. The conclusion is that the future of wave energy is in devices that are not simple monopoles or dipoles, but multi-body devices or other shapes equivalent to arrays.

  2. Key Aspects of Wave Energy

    DEFF Research Database (Denmark)

    Margheritini, Lucia; Nørgaard, Jørgen Harck

    2012-01-01

    . By collecting the experience from mainly three different wave energy developers, the possible alternative functions (other than energy production) of the devices are describe: Wave Dragon can be effectively used to reduce coastline erosion and/or as mussel farm; the Sea wave Slot cone Generator (SSG) can...

  3. Wave energy: a Pacific perspective.

    Science.gov (United States)

    Paasch, Robert; Ruehl, Kelley; Hovland, Justin; Meicke, Stephen

    2012-01-28

    This paper illustrates the status of wave energy development in Pacific rim countries by characterizing the available resource and introducing the region's current and potential future leaders in wave energy converter development. It also describes the existing licensing and permitting process as well as potential environmental concerns. Capabilities of Pacific Ocean testing facilities are described in addition to the region's vision of the future of wave energy.

  4. Wave Energy Study in China: Advancements and Perspectives

    Institute of Scientific and Technical Information of China (English)

    游亚戈; 郑永红; 沈永明; 吴必军; 刘荣

    2003-01-01

    The history and current status of research and development of wave energy in the world is briefly introduced. The main problems existing in these studies are pointed out. The description is focused on the current status and the advancements achieved in China. After analysis of the wave energy resources and practical situations in China, it is pointed out that the studies on wave energy should be not only concentrated on the conversion efficiency and costs of wave energy devices, but also focused on the technology of independent operation and stable output of electricity. Finally, the perspectives of application of wave energy in China are discussed.

  5. Critical point anomalies include expansion shock waves

    Energy Technology Data Exchange (ETDEWEB)

    Nannan, N. R., E-mail: ryan.nannan@uvs.edu [Mechanical Engineering Discipline, Anton de Kom University of Suriname, Leysweg 86, PO Box 9212, Paramaribo, Suriname and Process and Energy Department, Delft University of Technology, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Guardone, A., E-mail: alberto.guardone@polimi.it [Department of Aerospace Science and Technology, Politecnico di Milano, Via La Masa 34, 20156 Milano (Italy); Colonna, P., E-mail: p.colonna@tudelft.nl [Propulsion and Power, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)

    2014-02-15

    From first-principle fluid dynamics, complemented by a rigorous state equation accounting for critical anomalies, we discovered that expansion shock waves may occur in the vicinity of the liquid-vapor critical point in the two-phase region. Due to universality of near-critical thermodynamics, the result is valid for any common pure fluid in which molecular interactions are only short-range, namely, for so-called 3-dimensional Ising-like systems, and under the assumption of thermodynamic equilibrium. In addition to rarefaction shock waves, diverse non-classical effects are admissible, including composite compressive shock-fan-shock waves, due to the change of sign of the fundamental derivative of gasdynamics.

  6. Hydrodynamics of triangular-grid arrays of floating point-absorber wave energy converters with inter-body and bottom slack-mooring connections

    Energy Technology Data Exchange (ETDEWEB)

    Vicente, Pedro C.; Falcao, Antonio F. de O.; Gato, Luiz M.C. [IDMEC, Instituto Superior Tecnico, Technical University of Lisbon, 1049-001 Lisboa (Portugal); Justino, Paulo A.P. [Laboratorio Nacional de Energia e Geologia, 1649-038 Lisboa (Portugal)

    2009-07-01

    It may be convenient that dense arrays of floating point absorbers are spread-moored to the sea bottom through only some of their elements (possibly located in the periphery), while the other array elements are prevented from drifting and colliding with each other by connections to adjacent elements. An array of identical floating point absorbers located at the grid points of an equilateral triangular grid is considered in the paper. A spread set of slack-mooring lines connect the peripheric floaters to the bottom. A weight is located at the centre of each triangle whose function is o pull the three floaters towards each other and keep the inter-body moorings lines under tension. The whole system - buoys, moorings and power take-off systems - is assumed linear, so that a frequency domain analysis may be employed. Hydrodynamic interference between the oscillating bodies is neglected. Equations are presented for a set of three identical point absorbers. This is then extended to more complex equilateral iriangular grid arrays. Results from numerical simulations, with regular and irregular waves, are presented for the motions and power absorption of hemispherical converters in arrays of three and seven elements and different mooring and power take-off parameters, and wave incidence angles. Comparisons are given with the unmoored and independently-moored buoy situations.

  7. Key Aspects of Wave Energy

    DEFF Research Database (Denmark)

    Margheritini, Lucia; Nørgaard, Jørgen Harck

    2012-01-01

    Diversification of renewable energy sources is fundamental to ensure sustainability. In this contest, wave energy can provide a substantial contribution as soon as the sector breaks into the market. In order to accelerate shift from a technology to a market focus and reduce technical and non...... be used as a breakwater therefore providing a solid structure for harbor protection; the Wave Star can be used as a base for offshore wind and photovoltaic installation in the middle of the sea, realizing an hybrid renewable energy platform. It is the authors´ believe that taking wave energy devices......-technical risks, it is critical to provide comprehensive and reliable information on the technologies without neglecting attractive advantages. It is possible to underline a different key of lecture of wave energy performance by considering efficiency and power production as well as device versatility...

  8. Image processing to optimize wave energy converters

    Science.gov (United States)

    Bailey, Kyle Marc-Anthony

    The world is turning to renewable energies as a means of ensuring the planet's future and well-being. There have been a few attempts in the past to utilize wave power as a means of generating electricity through the use of Wave Energy Converters (WEC), but only recently are they becoming a focal point in the renewable energy field. Over the past few years there has been a global drive to advance the efficiency of WEC. Placing a mechanical device either onshore or offshore that captures the energy within ocean surface waves to drive a mechanical device is how wave power is produced. This paper seeks to provide a novel and innovative way to estimate ocean wave frequency through the use of image processing. This will be achieved by applying a complex modulated lapped orthogonal transform filter bank to satellite images of ocean waves. The complex modulated lapped orthogonal transform filterbank provides an equal subband decomposition of the Nyquist bounded discrete time Fourier Transform spectrum. The maximum energy of the 2D complex modulated lapped transform subband is used to determine the horizontal and vertical frequency, which subsequently can be used to determine the wave frequency in the direction of the WEC by a simple trigonometric scaling. The robustness of the proposed method is provided by the applications to simulated and real satellite images where the frequency is known.

  9. The SSG Wave Energy Converter

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Margheritini, Lucia; Kofoed, Jens Peter

    2012-01-01

    The Sea-wave Slot-cone Generator concept (SSG) is a Wave Energy Converter based on the wave overtopping principle utilizing several reservoirs placed on top of each other, in which the energy of the incoming wave will be stored as potential energy. The water captured in the reservoirs will then run...... through turbines for electricity production. The system utilizes a wide spectrum of different wave conditions by means of multiple reservoirs, located at different levels above the still water level. Thereby, it obtains a high overall efficiency and it can be suitable for shoreline and breakwater...... applications, presenting particular advantages such as: sharing structure costs, availability of grid connection and infrastructures, recirculation of water inside the harbor, as the outlet of the turbines is on the rear part of the system. Recently, plans for the SSG pilot installation were in progress...

  10. Tunnel effect wave energy detection

    Science.gov (United States)

    Kaiser, William J. (Inventor); Waltman, Steven B. (Inventor); Kenny, Thomas W. (Inventor)

    1995-01-01

    Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

  11. Wave energy converter test application

    OpenAIRE

    Hottola, Niko

    2016-01-01

    This thesis was made for wave energy company Wello Oy. Given assignment was to find the suitable generator and frequency converter for a wave energy converter test application. The primary objective was to find a suitable generator for direct drive, in order to avoid the weight of the test application rising too high. In this thesis the possible machine types for test application are presented and what are their advenatages and disadvantages. In addition, the operation of the frequency co...

  12. Wave Dragon Wave Energy Converters Used as Coastal Protection

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen Harck; Andersen, Thomas Lykke; Kofoed, Jens Peter

    2011-01-01

    This paper deals with wave energy converters used to reduce the wave height along shorelines. For this study the Wave Dragon wave energy converter is chosen. The wave height reduction from a single device has been evaluated from physical model tests in scale 1:51.8 of the 260 x 150 m, 24 kW/m model...

  13. Wave Dragon Wave Energy Converters Used as Coastal Protection

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen Harck; Andersen, Thomas Lykke; Kofoed, Jens Peter

    2011-01-01

    This paper deals with wave energy converters used to reduce the wave height along shorelines. For this study the Wave Dragon wave energy converter is chosen. The wave height reduction from a single device has been evaluated from physical model tests in scale 1:51.8 of the 260 x 150 m, 24 kW/m model...... Spain, to evaluate the potential for reducing wave heights close the shore by means of Wave Dragons....

  14. Proposed electromagnetic wave energy converter

    Science.gov (United States)

    Bailey, R. L.

    1973-01-01

    Device converts wave energy into electric power through array of insulated absorber elements responsive to field of impinging electromagnetic radiation. Device could also serve as solar energy converter that is potentially less expensive and fragile than solar cells, yet substantially more efficient.

  15. Direct Drive Wave Energy Buoy

    Energy Technology Data Exchange (ETDEWEB)

    Rhinefrank, Kenneth E. [Columbia Power Technologies, Inc.; Lenee-Bluhm, Pukha [Columbia Power Technologies, Inc.; Prudell, Joseph H. [Columbia Power Technologies, Inc.; Schacher, Alphonse A. [Columbia Power Technologies, Inc.; Hammagren, Erik J. [Columbia Power Technologies, Inc.; Zhang, Zhe [Columbia Power Technologies, Inc.

    2013-07-29

    The most prudent path to a full-scale design, build and deployment of a wave energy conversion (WEC) system involves establishment of validated numerical models using physical experiments in a methodical scaling program. This Project provides essential additional rounds of wave tank testing at 1:33 scale and ocean/bay testing at a 1:7 scale, necessary to validate numerical modeling that is essential to a utility-scale WEC design and associated certification.

  16. Wave energy resource in the Estaca de Bares area (Spain)

    Energy Technology Data Exchange (ETDEWEB)

    Iglesias, G.; Carballo, R. [Univ. of Santiago de Compostela, EPS, Hydraulic Eng., Campus Univ. s/n, 27002 Lugo (Spain)

    2010-07-15

    The area around Cape Estaca de Bares (the northernmost point of Iberia) presents a great potential for wave energy exploitation owing to its prominent position, with average deepwater wave power values exceeding 40 kW/m. The newly available SIMAR-44 dataset, composed of hindcast data spanning 44 years (1958-2001), is used alongside wave buoy data and numerical modelling to assess this substantial energy resource in detail. Most of the energy is provided by waves from the IV quadrant, generated by the prevailing westerlies blowing over the long Atlantic fetch. Combined scatter and energy diagrams are used to characterise the wave energy available in an average year in terms of the sea states involved. The lion's share is shown to correspond to significant wave heights between 2 and 5 m and energy periods between 11 and 14 s. The nearshore energy patterns are then examined using a coastal wave model (SWAN) with reference to four situations: average wave energy, growing wave energy (at the approach of a storm), extreme wave energy (at the peak of the storm) and decaying wave energy (as the storm recedes). The irregular bathymetry is found to produce local concentrations of wave energy in the nearshore between Cape Prior and Cape Ortegal and in front of Cape Estaca de Bares, with similar patterns (but varying wave power) in the four cases. These nearshore areas of enhanced wave energy are of the highest interest as prospective sites for a wave energy operation. The largest of them is directly in the lee of a large underwater mount west of Cape Ortegal. In sum, the Estaca de Bares area emerges as one of the most promising for wave energy exploitation in Europe. (author)

  17. Reliability of Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon

    . Structural reliability considerations and optimizations impact operation and maintenance (O&M) costs as well as the initial investment costs. Furthermore, there is a control system for WEC applications which defines the harvested energy but also the loads onto the structure. Therefore, extreme loads but also...... WEPTOS. Calibration of safety factors are performed for welded structures at theWavestar device including different control systems for harvesting energy from waves. In addition, a case study of different O&M strategies for WECs is discussed, and an example of reliability-based structural optimization......There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs to become successful and more competitive to other renewable electricity sources, the consideration of the structural reliability of WECs is essential...

  18. Reliability of Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon

    for welded structures at the Wavestar device includingdifferent control systems for harvesting energy from waves. In addition, a casestudy of different O&M strategies for WECs is discussed, and an example ofreliability-based structural optimization of the Wavestar foundation ispresented. The work performed......There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs tobecome successful and more competitive to other renewable electricity sources,the consideration of the structural reliability of WECs is essential.......Structural reliability considerations and optimizations impact operation andmaintenance (O&M) costs as well as the initial investment costs.Furthermore, there is a control system for WEC applications which defines theharvested energy but also the loads onto the structure. Therefore, extremeloads but also fatigue loads...

  19. Handbook of ocean wave energy

    CERN Document Server

    Kofoed, Jens

    2017-01-01

    This book is open access under a CC BY-NC 2.5 license. This book offers a concise, practice-oriented reference-guide to the field of ocean wave energy. The ten chapters highlight the key rules of thumb, address all the main technical engineering aspects and describe in detail all the key aspects to be considered in the techno-economic assessment of wave energy converters. Written in an easy-to-understand style, the book answers questions relevant to readers of different backgrounds, from developers, private and public investors, to students and researchers. It is thereby a valuable resource for both newcomers and experienced practitioners in the wave energy sector.

  20. Hydraulic behaviour of the floating wave energy converter Wave Dragon

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-07-01

    The objective of the project is to establish a scale 1:4.5 test model of the floating offshore wave energy converter - Wave Dragon - for testing at 5 m water depth in the Inlet Nissum Bredning. The test model will be equipped with an existing diameter 340 mm model turbine plus additional outlet tubes simulating the resistance from 1 - 16 turbines. The model will be designed to stay afloat even with a total loss of air pressure in the open bottom buoyancy chambers. The test series will primarily focus on measurements of hydraulic response, forces in the mooring system and overtopping quantities. Also data such as head, rotational speed and power production from the turbine will be monitored during the whole test period. The project will verify the effect of the pressured air buoyancy system, which cannot be scaled correctly in laboratory scale models. The test results will allow for an evaluation of the Wave Dragon power production as a function of sea state and freeboard height, in order to calibrate the existing WD-power simulation software. The model can be utilized for further testing of turbine regulation and stress and strain in the structure, establishing the necessary knowledge base for deploying a full-scale demonstration plant. This CD-ROM contains various videos, reports, notes, conference papers and Power Point presentations on the making of the wave energy converter Wave Dragon. (BA)

  1. Multisymplectic five-point scheme for the nonlinear wave equation

    Institute of Scientific and Technical Information of China (English)

    WANG Yushun; WANG Bin; YANG Hongwei; WANG Yunfeng

    2003-01-01

    In this paper, we introduce the multisymplectic structure of the nonlinear wave equation, and prove that the classical five-point scheme for the equation is multisymplectic. Numerical simulations of this multisymplectic scheme on highly oscillatory waves of the nonlinear Klein-Gordon equation and the collisions between kink and anti-kink solitons of the sine-Gordon equation are also provided. The multisymplectic schemes do not need to discrete PDEs in the space first as the symplectic schemes do and preserve not only the geometric structure of the PDEs accurately, but also their first integrals approximately such as the energy, the momentum and so on. Thus the multisymplectic schemes have better numerical stability and long-time numerical behavior than the energy-conserving scheme and the symplectic scheme.

  2. Zero Point Energy of Renormalized Wilson Loops

    OpenAIRE

    Hidaka, Yoshimasa; Pisarski, Robert D.

    2009-01-01

    The quark antiquark potential, and its associated zero point energy, can be extracted from lattice measurements of the Wilson loop. We discuss a unique prescription to renormalize the Wilson loop, for which the perturbative contribution to the zero point energy vanishes identically. A zero point energy can arise nonperturbatively, which we illustrate by considering effective string models. The nonperturbative contribution to the zero point energy vanishes in the Nambu model, but is nonzero wh...

  3. The Dynamics of Wave Energy

    OpenAIRE

    Ringwood, John

    2006-01-01

    This paper examines the challenges of efficiently harnessing wave energy. A variety of energy conversion device types is reviewed and a generic heaving buoy device selected for detailed examination. A number of modelling and control challenges are detailed and a hierarchical control structure is indicated. Both potable water production and electricity generation are included as possible uses of such devices and each presents separate control challenges.

  4. Handbook of Ocean Wave Energy

    DEFF Research Database (Denmark)

    of wave energy converters. Written in an easy-to-understand style, the book answers questions relevant to readers of different backgrounds, from developers, private and public investors, to students and researchers. It is thereby a valuable resource for both newcomers and experienced practitioners...

  5. Direct Drive Wave Energy Buoy

    Energy Technology Data Exchange (ETDEWEB)

    Rhinefrank, Kenneth [Columbia Power Technologies, Inc., Charlottesville, VA (United States); Lamb, Bradford [Columbia Power Technologies, Inc., Charlottesville, VA (United States); Prudell, Joseph [Columbia Power Technologies, Inc., Charlottesville, VA (United States); Hammagren, Erik [Columbia Power Technologies, Inc., Charlottesville, VA (United States); Lenee-Bluhm, Pukha [Columbia Power Technologies, Inc., Charlottesville, VA (United States)

    2016-08-22

    This Project aims to satisfy objectives of the DOE’s Water Power Program by completing a system detailed design (SDD) and other important activities in the first phase of a utility-scale grid-connected ocean wave energy demonstration. In early 2012, Columbia Power (CPwr) had determined that further cost and performance optimization was necessary in order to commercialize its StingRAY wave energy converter (WEC). CPwr’s progress toward commercialization, and the requisite technology development path, were focused on transitioning toward a commercial-scale demonstration. This path required significant investment to be successful, and the justification for this investment required improved annual energy production (AEP) and lower capital costs. Engineering solutions were developed to address these technical and cost challenges, incorporated into a proposal to the US Department of Energy (DOE), and then adapted to form the technical content and statement of project objectives of the resulting Project (DE-EE0005930). Through Project cost-sharing and technical collaboration between DOE and CPwr, and technical collaboration with Oregon State University (OSU), National Renewable Energy Lab (NREL) and other Project partners, we have demonstrated experimentally that these conceptual improvements have merit and made significant progress towards a certified WEC system design at a selected and contracted deployment site at the Wave Energy Test Site (WETS) at the Marine Corps Base in Oahu, HI (MCBH).

  6. Mathematical simulation of steep waves at a focus point

    Institute of Scientific and Technical Information of China (English)

    XU Li; ZHANG Min; WANG Yan-ying

    2007-01-01

    Mathematical models simulating steep waves at a focus point are presented in this paper. Simulations of extreme waves in a model basin were used to determine the loads on floating structures induced by the waves. Based on a new wave theory, numerical test results show that the simulation procedure is effective and the induced motion of water particles in the front of waves is an important factor influencing impact loads on floating bodies.

  7. Prototype Testing of the Wave Energy Converter Wave Dragon

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Frigaard, Peter; Friis-Madsen, Erik

    2006-01-01

    The Wave Dragon is an offshore wave energy converter of the overtopping type. It consists of two wave reflectors focusing the incoming waves towards a ramp, a reservoir for collecting the overtopping water and a number of hydro turbines for converting the pressure head into power. In the period...... from 1998 to 2001 extensive wave tank testing on a scale model was carried at Aalborg University. Then, a 57!27 m wide and 237 tonnes heavy (incl. ballast) prototype of the Wave Dragon, placed in Nissum Bredning, Denmark, was grid connected in May 2003 as the world’s first offshore wave energy...

  8. Prototype Testing of the Wave Energy Converter Wave Dragon

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Frigaard, Peter Bak; Friis-Madsen, Erik

    2004-01-01

    The Wave Dragon is an offshore wave energy converter of the overtopping type. It consists of two wave reflectors focusing the incoming waves towards a ramp, a reservoir for collecting the overtopping water and a number of hydro turbines for converting the pressure head into power. In the period...... from 1998 to 2001 extensive wave tank testing on a scale model was carried at Aalborg University. Then, a 57 x 27 m wide and 237 tonnes heavy (incl. ballast) prototype of the Wave Dragon, placed in Nissum Bredning, Denmark, was grid connected in May 2003 as the world's first offshore wave energy...

  9. Assessing wave energy effects on biodiversity: the wave hub experience.

    Science.gov (United States)

    Witt, M J; Sheehan, E V; Bearhop, S; Broderick, A C; Conley, D C; Cotterell, S P; Crow, E; Grecian, W J; Halsband, C; Hodgson, D J; Hosegood, P; Inger, R; Miller, P I; Sims, D W; Thompson, R C; Vanstaen, K; Votier, S C; Attrill, M J; Godley, B J

    2012-01-28

    Marine renewable energy installations harnessing energy from wind, wave and tidal resources are likely to become a large part of the future energy mix worldwide. The potential to gather energy from waves has recently seen increasing interest, with pilot developments in several nations. Although technology to harness wave energy lags behind that of wind and tidal generation, it has the potential to contribute significantly to energy production. As wave energy technology matures and becomes more widespread, it is likely to result in further transformation of our coastal seas. Such changes are accompanied by uncertainty regarding their impacts on biodiversity. To date, impacts have not been assessed, as wave energy converters have yet to be fully developed. Therefore, there is a pressing need to build a framework of understanding regarding the potential impacts of these technologies, underpinned by methodologies that are transferable and scalable across sites to facilitate formal meta-analysis. We first review the potential positive and negative effects of wave energy generation, and then, with specific reference to our work at the Wave Hub (a wave energy test site in southwest England, UK), we set out the methodological approaches needed to assess possible effects of wave energy on biodiversity. We highlight the need for national and international research clusters to accelerate the implementation of wave energy, within a coherent understanding of potential effects-both positive and negative.

  10. Reliability of Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon

    There are many different working principles for wave energy converters (WECs) which are used to produce electricity from waves. In order for WECs to become successful and more competitive to other renewable electricity sources, the consideration of the structural reliability of WECs is essential....... Structural reliability considerations and optimizations impact operation and maintenance (O&M) costs as well as the initial investment costs. Furthermore, there is a control system for WEC applications which defines the harvested energy but also the loads onto the structure. Therefore, extreme loads but also...... of the Wavestar foundation is presented. The work performed in this thesis focuses on the Wavestar and WEPTOS WEC devices which are only two working principles out of a large diversity. Therefore, in order to gain general statements and give advice for standards for structural WEC designs, more working principles...

  11. Wave-to-wire Modelling of Wave Energy Converters

    DEFF Research Database (Denmark)

    Ferri, Francesco

    , but talking about renewable energy partially ravels the problem out. Wave energy is a large, mostly untapped, renewable energy resource. It has the potential to contribute significantly to the future energy mix, but the sector has not yet rolled off into the market in consequence of a number of technical...... and non-technical issues. These can be efficiently summarised in the cost of the energy produced by the various wave energy converters: If compared with other renewable energy technologies the cost of energy from the ocean waves is still significantly higher. Holding the comparison it also important...... to noticed that there is not a clear front runner in the wave energy sector, which fades effort and funding over a too broad frame. In order to assist efficient development and analysis of wave energy converters and therefore to accelerate the sector progression towards commercialisation, a generally...

  12. Innovative Breakwaters Design for Wave Energy Conversion

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Stagonas, D.; Müller, G.

    2012-01-01

    This paper intends contributing to an economically and environmentally sustainable development of coastal infrastructures by investigating the possibility of combining together breakwaters and Wave Energy Converters (WEC). The latter change the wave energy to electricity, which may serve both the...

  13. Practical performances of MPC for wave energy converters

    DEFF Research Database (Denmark)

    Ferri, Francesco; Tetu, Amelie; Hals, J.

    2016-01-01

    Maximising the efficiency of Wave Energy Converter (WEC) is one of the important tasks toward the exploitation of the wave energy resource. Along with a proper design of the device, an important way to achieve better energy performances is to improve the wave-body interaction by applying...... version (1:20) of a single floater of the Wavestar WEC: a single degree of freedom point absorber. The system was tested with regular and irregular long crested waves in the deep basing at Aalborg University, DK and results of the MPC are compared with standard resistive controller architecture...

  14. Spin wave vortex from the scattering on Bloch point solitons

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho-Santos, V.L., E-mail: vagson.carvalho@usach.cl [Instituto Federal de Educação, Ciência e Tecnologia Baiano - Campus Senhor do Bonfim, Km 04 Estrada da Igara, 48970-000 Senhor do Bonfim, Bahia (Brazil); Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Elías, R.G., E-mail: gabriel.elias@usach.cl [Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Nunez, A.S., E-mail: alnunez@dfi.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 487-3, Santiago (Chile)

    2015-12-15

    The interaction of a spin wave with a stationary Bloch point is studied. The topological non-trivial structure of the Bloch point manifests in the propagation of spin waves endowing them with a gauge potential that resembles the one associated with the interaction of a magnetic monopole and an electron. By pursuing this analogy, we are led to the conclusion that the scattering of spin waves and Bloch points is accompanied by the creation of a magnon vortex. Interference between such a vortex and a plane wave leads to dislocations in the interference pattern that can be measurable by means of magnon holography.

  15. Short term wave forecasting, using digital filters, for improved control of Wave Energy Converters

    DEFF Research Database (Denmark)

    Tedd, James; Frigaard, Peter

    2007-01-01

    experimentally. Results are shown form measurements taken on the Wave Dragon prototype device, a floating overtopping device situated in Northern Denmark. In this case the method is able to accurately predict the surface elevation at the device 11.2 seconds before the measurement is made. This is sufficient......This paper presents a Digital Filter method for real time prediction of waves incident upon a Wave Energy device. The method transforms waves measured at a point ahead of the device, to expected waves incident on the device. The relationship between these incident waves and power capture is derived...

  16. Review Article: MHD Wave Propagation Near Coronal Null Points of Magnetic Fields

    Science.gov (United States)

    McLaughlin, J. A.; Hood, A. W.; de Moortel, I.

    2011-07-01

    We present a comprehensive review of MHD wave behaviour in the neighbourhood of coronal null points: locations where the magnetic field, and hence the local Alfvén speed, is zero. The behaviour of all three MHD wave modes, i.e. the Alfvén wave and the fast and slow magnetoacoustic waves, has been investigated in the neighbourhood of 2D, 2.5D and (to a certain extent) 3D magnetic null points, for a variety of assumptions, configurations and geometries. In general, it is found that the fast magnetoacoustic wave behaviour is dictated by the Alfvén-speed profile. In a β=0 plasma, the fast wave is focused towards the null point by a refraction effect and all the wave energy, and thus current density, accumulates close to the null point. Thus, null points will be locations for preferential heating by fast waves. Independently, the Alfvén wave is found to propagate along magnetic fieldlines and is confined to the fieldlines it is generated on. As the wave approaches the null point, it spreads out due to the diverging fieldlines. Eventually, the Alfvén wave accumulates along the separatrices (in 2D) or along the spine or fan-plane (in 3D). Hence, Alfvén wave energy will be preferentially dissipated at these locations. It is clear that the magnetic field plays a fundamental role in the propagation and properties of MHD waves in the neighbourhood of coronal null points. This topic is a fundamental plasma process and results so far have also lead to critical insights into reconnection, mode-coupling, quasi-periodic pulsations and phase-mixing.

  17. Zero-point energy in spheroidal geometries

    OpenAIRE

    Kitson, A. R.; Signal, A. I.

    2005-01-01

    We study the zero-point energy of a massless scalar field subject to spheroidal boundary conditions. Using the zeta-function method, the zero-point energy is evaluated for small ellipticity. Axially symmetric vector fields are also considered. The results are interpreted within the context of QCD flux tubes and the MIT bag model.

  18. Gravitational Zero Point Energy induces Physical Observables

    OpenAIRE

    Garattini, Remo

    2010-01-01

    We consider the contribution of Zero Point Energy on the induced Cosmological Constant and on the induced Electric/Magnetic charge in absence of matter fields. The method is applicable to every spherically symmetric background. Extensions to a generic $f(R) $ theory are also allowed. Only the graviton appears to be fundamental to the determination of Zero Point Energy.

  19. Review article: MHD wave propagation near coronal null points of magnetic fields

    CERN Document Server

    McLaughlin, J A; De Moortel, I; 10.1007/s11214-010-9654-y

    2010-01-01

    We present a comprehensive review of MHD wave behaviour in the neighbourhood of coronal null points: locations where the magnetic field, and hence the local Alfven speed, is zero. The behaviour of all three MHD wave modes, i.e. the Alfven wave and the fast and slow magnetoacoustic waves, has been investigated in the neighbourhood of 2D, 2.5D and (to a certain extent) 3D magnetic null points, for a variety of assumptions, configurations and geometries. In general, it is found that the fast magnetoacoustic wave behaviour is dictated by the Alfven-speed profile. In a $\\beta=0$ plasma, the fast wave is focused towards the null point by a refraction effect and all the wave energy, and thus current density, accumulates close to the null point. Thus, null points will be locations for preferential heating by fast waves. Independently, the Alfven wave is found to propagate along magnetic fieldlines and is confined to the fieldlines it is generated on. As the wave approaches the null point, it spreads out due to the di...

  20. Experimental Study on A Pendulum Wave Energy Converter

    Institute of Scientific and Technical Information of China (English)

    QIU Shou-qiang; YE Jia-wei; WANG Dong-jiao; LIANG Fu-lin

    2013-01-01

    Many of the existing wave energy converters (WEC) are of oscillating water column (OWC) and point absorber (PA) types.Fewer references have been published in public on the pendulum type WEC.A series of experimental tests on a bottom-hinged pendulum WEC model are carried out and some results are revealed in the present study.The purpose of this paper is to present a detailed description of the tests.It is found that wave energy conversion efficiency varies with the applied damping and wave conditions.In addition,special attention is given to the effect of the water ballast on the efficiency of the wave energy converter.It is demonstrated that the ballast plays an important role in energy extraction.Better understanding on how the performance of the device is influenced by damping,wave height,wave period and ballast is shown.

  1. The Crest Wing Wave Energy Device

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Antonishen, Michael Patrick

    This report presents the results of a continuation of an experimental study of the wave energy converting abilities of the Crest Wing wave energy converter (WEC), in the following referred to as ‘Phase 2'. The Crest Wing is a WEC that uses its movement in matching the shape of an oncoming wave...... to generate power. Model tests have been performed using scale models (length scale 1:30), provided by WaveEnergyFyn, in regular and irregular wave states that can be found in Assessment of Wave Energy Devices. Best Practice as used in Denmark (Frigaard et al., 2008). The tests were carried out at Dept....... of Civil Engineering, Aalborg University (AAU) in the 3D deep water wave tank. The displacement and force applied to a power take off system, provided by WaveEnergyFyn, were measured and used to calculate mechanical power available to the power take off....

  2. Nonlinear Alfvén wave dynamics at a 2D magnetic null point: ponderomotive force

    Science.gov (United States)

    Thurgood, J. O.; McLaughlin, J. A.

    2013-07-01

    Context. In the linear, β = 0 MHD regime, the transient properties of magnetohydrodynamic (MHD) waves in the vicinity of 2D null points are well known. The waves are decoupled and accumulate at predictable parts of the magnetic topology: fast waves accumulate at the null point; whereas Alfvén waves cannot cross the separatricies. However, in nonlinear MHD mode conversion can occur at regions of inhomogeneous Alfvén speed, suggesting that the decoupled nature of waves may not extend to the nonlinear regime. Aims: We investigate the behaviour of low-amplitude Alfvén waves about a 2D magnetic null point in nonlinear, β = 0 MHD. Methods: We numerically simulate the introduction of low-amplitude Alfvén waves into the vicinity of a magnetic null point using the nonlinear LARE2D code. Results: Unlike in the linear regime, we find that the Alfvén wave sustains cospatial daughter disturbances, manifest in the transverse and longitudinal fluid velocity, owing to the action of nonlinear magnetic pressure gradients (viz. the ponderomotive force). These disturbances are dependent on the Alfvén wave and do not interact with the medium to excite magnetoacoustic waves, although the transverse daughter becomes focused at the null point. Additionally, an independently propagating fast magnetoacoustic wave is generated during the early stages, which transports some of the initial Alfvén wave energy towards the null point. Subsequently, despite undergoing dispersion and phase-mixing due to gradients in the Alfvén-speed profile (∇cA ≠ 0) there is no further nonlinear generation of fast waves. Conclusions: We find that Alfvén waves at 2D cold null points behave largely as in the linear regime, however they sustain transverse and longitudinal disturbances - effects absent in the linear regime - due to nonlinear magnetic pressure gradients.

  3. Near-Shore Floating Wave Energy Converters

    DEFF Research Database (Denmark)

    Ruol, Piero; Zanuttigh, Barbara; Martinelli, Luca

    2011-01-01

    Aim of this note is to analyse the possible application of a Wave Energy Converter (WEC) as a combined tool to protect the coast and harvest energy. Physical model tests are used to evaluate wave transmission past a near-shore floating WEC of the wave activated body type, named DEXA. Efficiency...

  4. Experimental Study on the WavePiston Wave Energy Converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter; Angelelli, E.

    This report presents the results of an experimental study of the power performance of the WavePiston wave energy converter. It focuses mainly on evaluating the power generating capabilities of the device and the effect of the following issues: Scaling ratios PTO loading Wave height and wave period...... dependency Oblique incoming waves Distance between plates During the study, the model supplied by the client, WavePiston, has been rigorously tested as all the anticipated tests have been done thoroughly and during all tests, good quality data has been obtained from all the sensors....

  5. Magnetoacoustic Waves in Stratified Atmospheres with a Magnetic Null Point

    Science.gov (United States)

    Tarr, Lucas A.; Linton, Mark; Leake, James E.

    2016-05-01

    Magnetic fields strongly modify the propagation of MHD waves from the photosphere to the low corona, as can be shown exactly for the most simple case of a uniform magnetic field and isothermally stratrified atmosphere. For slightly more realistic scenarios, where both the atmospheric parameters and the magnetic field vary spatially, the linear MHD equations typically cannot be solved analytically. We use the Lagrangian Remap code--a nonlinear, shock-capturing MHD code--to study the propagation of initially acoustic wavepackets through a model 2D atmosphere that includes a gravitationally stratified chromosphere, transition region, and low corona. The magnetic field is formed by three photospheric concentrations and includes a single magnetic null point, resulting in an inhomogeneous system with a magnetic dome topology. A portion of an introduced wavepacket will refract toward the null due to the varying Alfven speed. Waves incident on the equipartition contour surrounding the null, where the sound and Alfven speeds coincide, partially transmit, reflect, and mode convert between branches of the local dispersion relation. Outward propagating slow modes generated during conversion become strongly concentrated along the set of field lines passing near the null. Acoustic energy is beamed back downwards towards each photospheric foot point, and upwards along one separatrix that exits the top of the numerical domain. Changes in the dominant restoring force for the wavepacket, between the Lorentz and pressure gradient forces, lead to a buildup of current density along topologically important features of the system (the null point and its four separatrices) and can drive reconnection at the null point itself. Ohmic dissipation of the currents locally heats the plasma. We find that the amount of current accumulation depends on where the centroid of a wavepacket initial crosses the photosphere, but does not simply coincide with regions of open versus closed magnetic field or

  6. Experiments on the WavePiston, Wave Energy Converter

    DEFF Research Database (Denmark)

    Angelelli, E.; Zanuttigh, B.; Kofoed, Jens Peter

    2011-01-01

    This paper analyses the performance of a new Wave Energy Converter (WEC) of the Oscillating Water Column type (OWC), named WavePiston. This near-shore floating device is composed of plates (i.e. energy collectors) sliding around a cylinder, that is placed perpendicular to the shore. Tests...

  7. Numerical Simulation of Spatial Lag Between Wave Breaking Point and Location of Maximum Wave-Induced Current

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jin-hai; TANG Yu

    2009-01-01

    A quasi three-dimensional numerical model of wave-driven coastal currents with the effects of surface rollers is developed for the study of the spatial lag between the location of the maximum wave-induced current and the wave breaking point.The governing equations are derived from Navier-Stokes equations and solved by the hybrid method combining the fractional step finite different method in the horizontal plane with a Galerkin finite element method in the vertical direction.The surface rollers effects are considered through incorporating the creation and evolution of the roller area into the free surface shear stress.An energy equation facilitates the computation process which transfers the wave breaking energy dissipation to the surface roller energy.The wave driver model is a phase-averaged wave model based on the wave action balance equation.Two sets of laboratory experiments producing breaking waves that generated longshore currents on a planar beach are used to evaluate the model's performance.The present wave-driven coastal current model with the roller effect in the surface shear stress term can produce satisfactory results by increasing the wave-induced nearshore current velocity inside the surf zone and shifting the location of the maximum longshore current velocity landward.

  8. Probabilistic Design of Wave Energy Devices

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Kofoed, Jens Peter; Ferreira, C.B.

    2011-01-01

    Wave energy has a large potential for contributing significantly to production of renewable energy. However, the wave energy sector is still not able to deliver cost competitive and reliable solutions. But the sector has already demonstrated several proofs of concepts. The design of wave energy...... and advocate for a probabilistic design approach, as it is assumed (in other areas this has been demonstrated) that this leads to more economical designs compared to designs based on deterministic methods. In the present paper a general framework for probabilistic design and reliability analysis of wave energy...

  9. Development of the Wave Energy Converter -Wave Dragon

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Frigaard, Peter; Sørensen, Hans Christian;

    2000-01-01

    2Over the years wave energy has gradually been brought into focus, as it has become clear that the fossil energy resources are limited, and cause large environmental problems, e.g. CO2 pollution. On this background a number of different wave energy converters have been proposed. In Denmark...... the government have decided to appropriate 20 mill. DKK (approx. 2,7 mill. EUR) to the development of wave energy devices over two years, 1998-1999, and the European Community (EC) also supports the development through the JOULECRAFT program....

  10. Hanstholm phase 2B. Offshore wave energy test 1994 - 1996

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-11-01

    The wave power converter consists of a float 2.5 meter in diameter, connected by a rope to a seabed-mounted piston pump, installed on 25 meter deep water 2,5 km offshore Hanstholm, Denmark. The converter is designed to absorb an average maximum power of 1 kW. Measured data in real sea conditions are compared to results based on computer simulations and previous tank testing. Losses caused by rope elasticity and hysteresis, friction in the pump and back flow through the valves are assessed. The economic perspectives of a large wave power plant are presented, based on a revised prototype incorporating the results and experience gained during the test period. The wave energy conversion test `Hanstholm phase 2B` has showed, that it it technically possible to exploit the offshore wave energy resource. This source of energy could become attractive for commercial enterprise. The wave power converter demonstrated a reliable performance over a period of nine months. It produced energy under all wave conditions and survived storm waves of 9,6 m. A 300 MW wave power plant in the Danish part of the North sea is estimated to produce electricity at a cost between 2,1 - 2,4 DKK/kWh. The electrical transmission to shore contribute to approximately 20% of the cost. New data predict a potential of 23 kW per meter wave front. The energy plan Energy 21 proposed by the Danish Department of Energy, includes a scenario incorporating wave energy in the energy system year 2030. A strategy for the development of wave energy, has been proposed as part of the project OWEC-1 supported by the European Joule R and D programme. A proposal for future Danish initiatives to develop second generation point absorber systems is outlined. (ARW) 29 refs.

  11. Offshore Desalination Using Wave Energy

    Directory of Open Access Journals (Sweden)

    Álvaro Serna

    2013-01-01

    Full Text Available This paper evaluates the design of an offshore desalination plant currently under preliminary development. The purpose is to test the feasibility of producing drinkable water using wave energy in out-of-sight installations, as an alternative for those locations where land use, civil engineering works, and/or environmental impact make a coast-based solution inadequate. After describing the components, a proposal for sizing them is studied, based on using buoy-measured data at the expected location and their mathematical models of the different sections of the plant. Finally, by using measured buoy data, the influence of sizing on the expected performance is studied for a specific location, and one of the designs is developed in detail.

  12. Ocean floor mounting of wave energy converters

    Science.gov (United States)

    Siegel, Stefan G

    2015-01-20

    A system for mounting a set of wave energy converters in the ocean includes a pole attached to a floor of an ocean and a slider mounted on the pole in a manner that permits the slider to move vertically along the pole and rotate about the pole. The wave energy converters can then be mounted on the slider to allow adjustment of the depth and orientation of the wave energy converters.

  13. Testing, Analysis and Control of Wave Dragon, Wave Energy Converter

    DEFF Research Database (Denmark)

    Tedd, James

    of a textbook, a submitted journal paper and three peer-reviewed conference papers. The content can be broadly divided into four topics: experiences gained with the Wave Dragon prototype device; power-production verification; overtopping analysis; and improvements in control. A comprehensive record...... the expected performance. Other sources of generation are presented, including development and tank testing of a novel power absorbing joint. Wave Dragon belongs in the family of overtopping wave energy converters. The energy is captured by waves running up a ramp and overtopping the crest into a reservoir...

  14. Wave energy input into the Ekman layer

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This paper is concerned with the wave energy input into the Ekman layer, based on 3 observational facts that surface waves could significantly affect the profile of the Ekman layer. Under the assumption of constant vertical diffusivity, the analytical form of wave energy input into the Ekman layer is derived. Analysis of the energy balance shows that the energy input to the Ekman layer through the wind stress and the interaction of the Stokes-drift with planetary vorticity can be divided into two kinds. One is the wind energy input, and the other is the wave energy input which is dependent on wind speed, wave characteristics and the wind direction relative to the wave direction. Estimates of wave energy input show that wave energy input can be up to 10% in high-latitude and high-wind speed areas and higher than 20% in the Antarctic Circumpolar Current, compared with the wind energy input into the classical Ekman layer. Results of this paper are of significance to the study of wave-induced large scale effects.

  15. Energy flow, energy density of Timoshenko beam and wave mode incoherence

    Science.gov (United States)

    Zhou, Jun; Rao, Zhushi; Ta, Na

    2015-10-01

    Time-averaged energy flow and energy density are of significance in vibration analysis. The wave decomposition method is more fruitful and global in physical sense than the state variables depicted point by point. By wave approach, the Timoshenko beam vibration field is decomposed into two distinct modes: travelling and evanescent waves. Consequently, the power and energy functions defined on these waves' amplitude and phase need to be established. However, such formulas on Timoshenko beam are hardly found in literatures. Furthermore, the incoherence between these two modes is of theoretical and practical significance. This characteristic guarantees that the resultant power or energy of a superposed wave field is equal to the sum of the power or energy that each wave mode would generate individually. Unlike Euler-Bernoulli beam, such incoherence in the Timoshenko beam case has not been theoretically proved so far. Initially, the power and energy formulas based on wave approach and the corresponding incoherence proof are achieved by present work, both in theoretical and numerical ways. Fortunately, the theoretical and numerical results show that the travelling and evanescent wave modes are incoherent with each other both on power and energy functions. Notably, the energy function is unconventional and self-defined in order to obtain the incoherence. Some remarkable power transmission characteristics of the evanescent wave are also illustrated meanwhile.

  16. Investigation of Wave Transmission from a Floating Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen Harck; Andersen, Thomas Lykke

    2012-01-01

    This paper focuses on the calibration of the MIKE21BW model against the measured wave height reduction behind a 24 kW/m Wave Dragon (WD) wave energy converter. A numerical model is used to determine the wave transmission through the floating WD in varying wave conditions. The transmission obtained...

  17. Catching the right wave: evaluating wave energy resources and potential compatibility with existing marine and coastal uses.

    Science.gov (United States)

    Kim, Choong-Ki; Toft, Jodie E; Papenfus, Michael; Verutes, Gregory; Guerry, Anne D; Ruckelshaus, Marry H; Arkema, Katie K; Guannel, Gregory; Wood, Spencer A; Bernhardt, Joanna R; Tallis, Heather; Plummer, Mark L; Halpern, Benjamin S; Pinsky, Malin L; Beck, Michael W; Chan, Francis; Chan, Kai M A; Levin, Phil S; Polasky, Stephen

    2012-01-01

    Many hope that ocean waves will be a source for clean, safe, reliable and affordable energy, yet wave energy conversion facilities may affect marine ecosystems through a variety of mechanisms, including competition with other human uses. We developed a decision-support tool to assist siting wave energy facilities, which allows the user to balance the need for profitability of the facilities with the need to minimize conflicts with other ocean uses. Our wave energy model quantifies harvestable wave energy and evaluates the net present value (NPV) of a wave energy facility based on a capital investment analysis. The model has a flexible framework and can be easily applied to wave energy projects at local, regional, and global scales. We applied the model and compatibility analysis on the west coast of Vancouver Island, British Columbia, Canada to provide information for ongoing marine spatial planning, including potential wave energy projects. In particular, we conducted a spatial overlap analysis with a variety of existing uses and ecological characteristics, and a quantitative compatibility analysis with commercial fisheries data. We found that wave power and harvestable wave energy gradually increase offshore as wave conditions intensify. However, areas with high economic potential for wave energy facilities were closer to cable landing points because of the cost of bringing energy ashore and thus in nearshore areas that support a number of different human uses. We show that the maximum combined economic benefit from wave energy and other uses is likely to be realized if wave energy facilities are sited in areas that maximize wave energy NPV and minimize conflict with existing ocean uses. Our tools will help decision-makers explore alternative locations for wave energy facilities by mapping expected wave energy NPV and helping to identify sites that provide maximal returns yet avoid spatial competition with existing ocean uses.

  18. Catching the right wave: evaluating wave energy resources and potential compatibility with existing marine and coastal uses.

    Directory of Open Access Journals (Sweden)

    Choong-Ki Kim

    Full Text Available Many hope that ocean waves will be a source for clean, safe, reliable and affordable energy, yet wave energy conversion facilities may affect marine ecosystems through a variety of mechanisms, including competition with other human uses. We developed a decision-support tool to assist siting wave energy facilities, which allows the user to balance the need for profitability of the facilities with the need to minimize conflicts with other ocean uses. Our wave energy model quantifies harvestable wave energy and evaluates the net present value (NPV of a wave energy facility based on a capital investment analysis. The model has a flexible framework and can be easily applied to wave energy projects at local, regional, and global scales. We applied the model and compatibility analysis on the west coast of Vancouver Island, British Columbia, Canada to provide information for ongoing marine spatial planning, including potential wave energy projects. In particular, we conducted a spatial overlap analysis with a variety of existing uses and ecological characteristics, and a quantitative compatibility analysis with commercial fisheries data. We found that wave power and harvestable wave energy gradually increase offshore as wave conditions intensify. However, areas with high economic potential for wave energy facilities were closer to cable landing points because of the cost of bringing energy ashore and thus in nearshore areas that support a number of different human uses. We show that the maximum combined economic benefit from wave energy and other uses is likely to be realized if wave energy facilities are sited in areas that maximize wave energy NPV and minimize conflict with existing ocean uses. Our tools will help decision-makers explore alternative locations for wave energy facilities by mapping expected wave energy NPV and helping to identify sites that provide maximal returns yet avoid spatial competition with existing ocean uses.

  19. Energy in a String Wave

    Science.gov (United States)

    Ng, Chiu-king

    2010-01-01

    When one end of a taut horizontal elastic string is shaken repeatedly up and down, a transverse wave (assume sine waveform) will be produced and travel along it. College students know this type of wave motion well. They know when the wave passes by, each element of the string will perform an oscillating up-down motion, which in mechanics is termed…

  20. Wave energy potential in Galicia (NW Spain)

    DEFF Research Database (Denmark)

    Iglesias, Gregorio; López, Mario; Carballo, Rodrigo;

    2009-01-01

    Wave power presents significant advantages with regard to other CO2-free energy sources, among which the predictability, high load factor and low visual and environmental impact stand out. Galicia, facing the Atlantic on the north-western corner of the Iberian Peninsula, is subjected to a very...... harsh wave climate; in this work its potential for energy production is assessed based on three-hourly data from a third generation ocean wave model (WAM) covering the period 1996 - 2005. Taking into account the results of this assessment along with other relevant considerations such as the location...... of ports, navigation routes, and fishing and aquaculture zones, an area is selected for wave energy exploitation. The transformation of the offshore wave field as it propagates into this area is computed by means of a nearshore wave model (SWAN) in order to select the optimum locations for a wave farm. Two...

  1. Performance Evaluation of Wave Energy Converters

    DEFF Research Database (Denmark)

    Pecher, Arthur

    Ocean waves provide a sustainable, power-dense, predictable and widely available source of energy that could provide about 10 % of worlds energy needs. While research into wave energy has been undertaken for decades, a significant increase in related activities has been seen in the recent years......, with more than 150 concepts currently being developed worldwide. Wave energy conversion concepts can be of many kinds, as the energy in the waves can be absorbed in many different ways. However, each concept is expected to require a thorough development process, involving different phases and prototypes....... Guidelines for the development of wave energy converters recommend the use of different prototypes, having different sizes, which have to perform tank tests or sea trials. This implicates the need of different testing environment, which shifts from being controllable to uncontrollable with the development...

  2. Transmission of wave energy in curved ducts

    Science.gov (United States)

    Rostafinski, W.

    1973-01-01

    A formation of wave energy flow was developed for motion in curved ducts. A parametric study over a range of frequencies determined the ability of circular bends to transmit energy for the case of perfectly rigid walls.

  3. Levelized Cost of Energy of the Weptos wave energy converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter

    This report presents the cost of energy calculations of a wave energy array of 90 MW, consisting of 25 x 3.6 MW Weptos wave energy converters. The calculation has been made in analogy with a publically available document presented by the UK government, covering the case of a similar size wind...

  4. Predictability of Wave Energy and Electricity Markets

    DEFF Research Database (Denmark)

    Chozas, Julia Fernandez

    2012-01-01

    The articlw addresses an important challenge ahead the integration of the electricity generated by wave energy conversion technologies into the electric grid. Particularly, it looks into the role of wave energy within the day-ahead electricity market. For that the predictability of the theoretical...... power outputs of three wave energy technologies in the Danish North Sea are examined. The simultaneous and co-located forecast and buoy-measured wave parameters at Hanstholm, Denmark, during a non-consecutive autumn and winter 3-month period form the basis of the investigation. The objective...

  5. Model Predictive Control of a Wave Energy Converter

    DEFF Research Database (Denmark)

    Andersen, Palle; Pedersen, Tom Søndergård; Nielsen, Kirsten Mølgaard;

    2015-01-01

    In this paper reactive control and Model Predictive Control (MPC) for a Wave Energy Converter (WEC) are compared. The analysis is based on a WEC from Wave Star A/S designed as a point absorber. The model predictive controller uses wave models based on the dominating sea states combined with a model...... connecting undisturbed wave sequences to sequences of torque. Losses in the conversion from mechanical to electrical power are taken into account in two ways. Conventional reactive controllers are tuned for each sea state with the assumption that the converter has the same efficiency back and forth. MPC...

  6. Power Collection from Wave Energy Farms

    Directory of Open Access Journals (Sweden)

    Marta Molinas

    2013-04-01

    Full Text Available Most Wave Energy Converters (WECs produce highly distorted power due to thereciprocal motion induced by ocean waves. Some WEC systems have integrated energystorage that overcomes this limitation, but add significant expenses to an already costlysystem. As an alternative approach, this article investigates the direct export option thatrelies on aggregate smoothing among several WECs. By optimizing the positioning of theWEC devices with respect to the incoming waves, fluctuations may be mutually canceledout between the devices. This work is based on Fred. Olsen’s WEC system Lifesaver, anda WEC farm consisting of 48 devices is designed in detail and simulated. The major costdriver for the electrical export system is the required oversize factor necessary for transferof the average power output. Due to the low power quality, this number can be as high as20 at the entry point of the electrical system, and it is thus crucial to quickly improve thepower quality so that the downstream power system is efficiently utilized. The simulationsundertaken in this work indicate that a high quality power output can be achieved at the farmlevel, but that a significant oversize factor will be required in the intermediate power systemwithin the farm.

  7. Energy in one-dimensional linear waves

    Energy Technology Data Exchange (ETDEWEB)

    Repetto, C E; Roatta, A; Welti, R J, E-mail: welti@fceia.unr.edu.ar [Laboratorio de Vibraciones y Ondas, Departamento de Fisica, Escuela de Formacion Basica, Facultad de Ciencias Exactas, IngenierIa y Agrimensura (UNR), Pellegrini 250, S2000BTP Rosario (Argentina)

    2011-11-15

    This work is based on propagation phenomena that conform to the classical wave equation. General expressions of power, the energy conservation equation in continuous media and densities of the kinetic and potential energies are presented. As an example, we study the waves in a string and focused attention on the case of standing waves. The treatment is applicable to introductory science textbooks. (letters and comment)

  8. Reliability assessment of wave Energy devices

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kramer, Morten; Kofoed, Jens Peter

    2014-01-01

    Energy from waves may play a key role in sustainable electricity production in the future. Optimal reliability levels for components used for Wave Energy Devices (WEDs) need to be defined to be able to decrease their cost of electricity. Optimal reliability levels can be found using probabilistic...

  9. Predictability of Wave Energy and Electricity Markets

    DEFF Research Database (Denmark)

    Chozas, Julia Fernandez

    2012-01-01

    The articlw addresses an important challenge ahead the integration of the electricity generated by wave energy conversion technologies into the electric grid. Particularly, it looks into the role of wave energy within the day-ahead electricity market. For that the predictability of the theoretical...

  10. Annular wave packets at Dirac points and probability oscillation in graphene

    CERN Document Server

    Luo, Ji; Valencia, Daniel

    2011-01-01

    Wave packets in graphene whose central wave vector is at Dirac points are investigated by numerical calculations. Starting from an initial Gaussian function, these wave packets form into annular peaks that propagate to all directions like ripple-rings on water surface. At the beginning, electronic probability alternates between the central peak and the ripple-rings and transient oscillation occurs at the center. As time increases, the ripple-rings propagate at the fixed Fermi speed, and their widths remain unchanged. The axial symmetry of the energy dispersion leads to the circular symmetry of the wave packets. The fixed speed and widths, however, are attributed to the linearity of the energy dispersion. Interference between states that respectively belong to two branches of the energy dispersion leads to multiple ripple-rings and the probability-density oscillation. In a magnetic field, annular wave packets become confined and no longer propagate to infinity. If the initial Gaussian width differs greatly fro...

  11. Prototype testing of the wave energy converter wave dragon

    Energy Technology Data Exchange (ETDEWEB)

    Kofoed, Jens Peter; Frigaard, Peter [Hydraulics and Coastal Engineering Laboratory, Department of Civil Engineering, Aalborg University, Sohngaardsholmsvej 57, Aalborg 9000 (Denmark); Friis-Madsen, Erik [Loewenmark F.R.I., Copenhagen (Denmark); Soerensen, Hans Chr. [SPOK, Copenhagen (Denmark)

    2006-02-01

    The Wave Dragon is an offshore wave energy converter of the overtopping type. It consists of two wave reflectors focusing the incoming waves towards a ramp, a reservoir for collecting the overtopping water and a number of hydro turbines for converting the pressure head into power. In the period from 1998 to 2001 extensive wave tank testing on a scale model was carried at Aalborg University. Then, a 57x27m wide and 237tonnes heavy (incl. ballast) prototype of the Wave Dragon, placed in Nissum Bredning, Denmark, was grid connected in May 2003 as the world's first offshore wave energy converter. The prototype is fully equipped with hydro turbines and automatic control systems, and is instrumented in order to monitor power production, wave climate, forces in mooring lines, stresses in the structure and movements of the Wave Dragon. In the period May 2003 to January 2005 an extensive measuring program has been carried out, establishing the background for optimal design of the structure and regulation of the power take off system. Planning for deployment of a 4MW power production unit in the Atlantic by 2007 is in progress. (author)

  12. Diffuse Waves and Energy Densities Near Boundaries

    Science.gov (United States)

    Sanchez-Sesma, F. J.; Rodriguez-Castellanos, A.; Campillo, M.; Perton, M.; Luzon, F.; Perez-Ruiz, J. A.

    2007-12-01

    Green function can be retrieved from averaging cross correlations of motions within a diffuse field. In fact, it has been shown that for an elastic inhomogeneous, anisotropic medium under equipartitioned, isotropic illumination, the average cross correlations are proportional to the imaginary part of Green function. For instance coda waves are due to multiple scattering and their intensities follow diffusive regimes. Coda waves and the noise sample the medium and effectively carry information along their paths. In this work we explore the consequences of assuming both source and receiver at the same point. From the observable side, the autocorrelation is proportional to the energy density at a given point. On the other hand, the imaginary part of the Green function at the source itself is finite because the singularity of Green function is restricted to the real part. The energy density at a point is proportional with the trace of the imaginary part of Green function tensor at the source itself. The Green function availability may allow establishing the theoretical energy density of a seismic diffuse field generated by a background equipartitioned excitation. We study an elastic layer with free surface and overlaying a half space and compute the imaginary part of the Green function for various depths. We show that the resulting spectrum is indeed closely related to the layer dynamic response and the corresponding resonant frequencies are revealed. One implication of present findings lies in the fact that spatial variations may be useful in detecting the presence of a target by its signature in the distribution of diffuse energy. These results may be useful in assessing the seismic response of a given site if strong ground motions are scarce. It suffices having a reasonable illumination from micro earthquakes and noise. We consider that the imaginary part of Green function at the source is a spectral signature of the site. The relative importance of the peaks of

  13. Zero-point energy of confined fermions

    Energy Technology Data Exchange (ETDEWEB)

    Milton, K.A.

    1980-01-01

    A closed form for the reduced Green's function of massless fermions in the interior of a spherical bag is obtained. In terms of this Green's function, the corresponding zero-point or Casimir energy is computed. It is proposed that a resulting quadratic divergence can be absorbed by renormalizing a suitable parameter in the bag model (that is, absorbed by a contact term). The residual Casimir stress is attractive, but smaller than the repulsive Casimir stress of gluons in the model. The result for the total zero-point energy is in substantial disagreement with bag model phenomenological values.

  14. Capturing rogue waves by multi-point statistics

    CERN Document Server

    Hadjihosseini, Ali; Hoffmann, Norbert P; Peinke, Joachim

    2015-01-01

    As an example for complex systems with extreme events we investigate ocean wave states exhibiting rogue waves. We present a statistical method of data analysis based on multi-point statistics which for the first time allows grasping extreme rogue wave events in a statistically highly satisfactory manner. The key to the success of the approach is mapping the complexity of multi-point data onto the statistics of hierarchically ordered height increments for different time scales for which we can show that a stochastic cascade process with Markov properties is governed by a Fokker-Planck equation. Conditional probabilities as well as the Fokker-Planck equation itself can be estimated directly from the available observational data. With this stochastic description surrogate data sets can in turn be generated allowing to work out arbitrary statistical features of the complex sea state in general and extreme rogue wave events in particular. The results also open up new perspectives for forecasting the occurrence pro...

  15. Research on Energy Conversion System of Floating Wave Energy Converter

    Institute of Scientific and Technical Information of China (English)

    张亚群; 盛松伟; 游亚戈; 吴必军; 刘洋

    2014-01-01

    A wave power device includes an energy harvesting system and a power take-off system. The power take-off system of a floating wave energy device is the key that converts wave energy into other forms. A set of hydraulic power take-off system, which suits for the floating wave energy devices, includes hydraulic system and power generation system. The hydraulic control system uses a special“self-hydraulic control system”to control hydraulic system to release or save energy under the maximum and the minimum pressures. The maximum pressure is enhanced to 23 MPa, the minimum to 9 MPa. Quite a few experiments show that the recent hydraulic system is evidently improved in efficiency and reliability than our previous one, that is expected to be great significant in the research and development of our prototype about wave energy conversion.

  16. Energy Capture Optimization for an Adaptive Wave Energy Converter

    NARCIS (Netherlands)

    Barradas Berglind, Jose de Jesus; Meijer, Harmen; van Rooij, Marijn; Clemente Pinol, Silvia; Galvan Garcia, Bruno; Prins, Wouter; Vakis, Antonis I.; Jayawardhana, Bayu

    2016-01-01

    Wave energy has great potential as a renewable energy source, and can therefore contribute significantly to the proportion of renewable energy in the global energy mix. This is especially important since energy mixes with high renewable penetration have become a worldwide priority. One solution to f

  17. Wave energy resource assessment for the Indian shelf seas

    Digital Repository Service at National Institute of Oceanography (India)

    SanilKumar, V.; Anoop, T.R.

    As a renewable energy, the assessment of wave power potential around a country is crucial. Knowledge of the temporal and spatial variations of wave energy is required for locating a wave power plant. This study investigates the variations in wave...

  18. Energy cascade in internal wave attractors

    CERN Document Server

    Brouzet, Christophe; Joubaud, Sylvain; Sibgatullin, Ilias; Dauxois, Thierry

    2016-01-01

    One of the pivotal questions in the dynamics of the oceans is related to the cascade of mechanical energy in the abyss and its contribution to mixing. Here, we propose internal wave attractors in the large amplitude regime as a unique self-consistent experimental and numerical setup that models a cascade of triadic interactions transferring energy from large-scale monochro-matic input to multi-scale internal wave motion. We also provide signatures of a discrete wave turbulence framework for internal waves. Finally, we show how beyond this regime, we have a clear transition to a regime of small-scale high-vorticity events which induce mixing. Introduction.

  19. Zero Point Energy and the Dirac Equation

    DEFF Research Database (Denmark)

    Forouzbakhsh, Farshid

    2007-01-01

    Zero Point Energy (ZPE) describes the random electromagnetic oscillations that are left in the vacuum after all other energy has been removed. One way to explain this is by means of the uncertainty principle of quantum physics, which implies that it is impossible to have a zero energy condition. I...... this article, the ZPE is explained by using a novel description of the graviton. This is based on the behavior of photons in gravitational field, leading to a new definition of the graviton. In effect, gravitons behave as if they have charge and magnetic effects. These are referred to as negative color charge...

  20. Design and Control of Full Scale Wave Energy Simulator System

    DEFF Research Database (Denmark)

    Pedersen, Henrik C.; Hansen, Anders Hedegaard; Hansen, Rico Hjerm

    2012-01-01

    For wave energy to become feasible it is a requirement that the efficiency and reliability of the power take-off (PTO) systems are significantly improved. The cost of installing and testing PTO-systems at sea are however very high, and the focus of the current paper is therefore on the design...... of a full scale wave simulator for testing PTO-systems for point absorbers. The main challenge is here to design a system, which mimics the behavior of a wave when interacting with a given PTO-system. The paper includes a description of the developed system, located at Aalborg University......, and the considerations behind the design. Based on the description a model of the system is presented, which, along with a description of the wave theory applied, makes the foundation for the control strategy. The objective of the control strategy is to emulate not only the wave behavior, but also the dynamic wave...

  1. Performance Evaluation of Wave Energy Converters

    DEFF Research Database (Denmark)

    Pecher, Arthur

    Ocean waves provide a sustainable, power-dense, predictable and widely available source of energy that could provide about 10 % of worlds energy needs. While research into waveenergy has been undertaken for decades, a significant increase in related activities has been seen in the recent years......, with more than 150 concepts currently being developed worldwide. Wave energy conversion concepts can be of many kinds, as the energy in the waves can be absorbed in many different ways. However, each concept is expected to require a thorough development process, involving different phases and prototypes....... Guidelines for the development of wave energy converters recommend the use of different prototypes, having different sizes, which have to perform tank tests or sea trials. Thisimplicates the need of different testing environment, which shifts from being controllable to uncontrollable with the development...

  2. Hydraulic Response of the Wave Energy Converter Wave Dragon in Nissum Bredning

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Frigaard, Peter

    This report deals with the hydraulic performance of the wave energy converter Wave Dragon, Nissum Bredning prototype.......This report deals with the hydraulic performance of the wave energy converter Wave Dragon, Nissum Bredning prototype....

  3. Momentum and energy transport by waves in the solar atmosphere and solar wind

    Science.gov (United States)

    Jacques, S. A.

    1977-01-01

    The fluid equations for the solar wind are presented in a form which includes the momentum and energy flux of waves in a general and consistent way. The concept of conservation of wave action is introduced and is used to derive expressions for the wave energy density as a function of heliocentric distance. The explicit form of the terms due to waves in both the momentum and energy equations are given for radially propagating acoustic, Alfven, and fast mode waves. The effect of waves as a source of momentum is explored by examining the critical points of the momentum equation for isothermal spherically symmetric flow. We find that the principal effect of waves on the solutions is to bring the critical point closer to the sun's surface and to increase the Mach number at the critical point. When a simple model of dissipation is included for acoustic waves, in some cases there are multiple critical points.

  4. Investigation of Wave Transmission from a Floating Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen Harck; Andersen, Thomas Lykke

    2012-01-01

    This paper focuses on the calibration of the MIKE21BW model against the measured wave height reduction behind a 24 kW/m Wave Dragon (WD) wave energy converter. A numerical model is used to determine the wave transmission through the floating WD in varying wave conditions. The transmission obtained...... from the MIKE21BW model is compared to results from a simpler model, based on the integration of wave energy flux. The conclusion is that the simplified approach provides results similar to the transmission obtained from the numerical model, both for a single WD and a farm of multiple WDs....

  5. Development of the Wave Energy Converter

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Frigaard, Peter; Sørensen, Hans Christian

    2000-01-01

    The development of the wave energy converter Wave Dragon (WD) is presented. The WD is based on the overtopping principle. Initially a description of the WD is given. Then the development over time in terms of the various research and development projects working with the concept is described...

  6. Short term wave forecasting, using digital filters, for improved control of Wave Energy Converters

    Energy Technology Data Exchange (ETDEWEB)

    Tedd, J.; Frigaard, P. [Department of Civil Engineering, Aalborg University, Aalborg (Denmark)

    2007-07-01

    This paper presents a Digital Filter method for real time prediction of waves incident upon a Wave Energy device. The method transforms waves measured at a point ahead of the device, to expected waves incident on the device. The relationship between these incident waves and power capture is derived experimentally. Results are shown form measurements taken on the Wave Dragon prototype device, a floating overtopping device situated in Northern Denmark. In this case the method is able to accurately predict the surface elevation at the device 11.2 seconds before the measurement is made. This is sufficient to allow advanced control systems to be developed using this knowledge to significantly improve power capture.

  7. Energy Extraction from a Slider-Crank Wave Energy under Irregular Wave Conditions: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Yuanrui; Karayaka, H. Bora; Yan, Yanjun; Zhang, James Z.; Muljadi, Eduard; Yu, Yi-Hsiang

    2015-08-24

    A slider-crank wave energy converter (WEC) is a novel energy conversion device. It converts wave energy into electricity at a relatively high efficiency, and it features a simple structure. Past analysis on this particular WEC has been done under regular sinusoidal wave conditions, and suboptimal energy could be achieved. This paper presents the analysis of the system under irregular wave conditions; a time-domain hydrodynamics model is adopted and a rule-based control methodology is introduced to better serve the irregular wave conditions. Results from the simulations show that the performance of the system under irregular wave conditions is different from that under regular sinusoidal wave conditions, but a reasonable amount of energy can still be extracted.

  8. Power Generation Using Mechanical Wave Energy Converter

    Directory of Open Access Journals (Sweden)

    Srinivasan Chandrasekaran

    2012-03-01

    Full Text Available Ocean wave energy plays a significant role in meeting the growing demand of electric power. Economic, environmental, and technical advantages of wave energy set it apart from other renewable energy resources. Present study describes a newly proposed Mechanical Wave Energy Converter (MEWC that is employed to harness heave motion of floating buoy to generate power. Focus is on the conceptual development of the device, illustrating details of component level analysis. Employed methodology has many advantages such as i simple and easy fabrication; ii easy to control the operations during rough weather; and iii low failure rate during normal sea conditions. Experimental investigations carried out on the scaled model of MWEC show better performance and its capability to generate power at higher efficiency in regular wave fields. Design Failure Mode and Effect Analysis (FMEA shows rare failure rates for all components except the floating buoy.

  9. State estimation for wave energy converters

    Energy Technology Data Exchange (ETDEWEB)

    Bacelli, Giorgio; Coe, Ryan Geoffrey

    2017-04-01

    This report gives a brief discussion and examples on the topic of state estimation for wave energy converters (WECs). These methods are intended for use to enable real-time closed loop control of WECs.

  10. Hydraulic power take-off for wave energy systems

    DEFF Research Database (Denmark)

    Christensen, Georg Kronborg

    2001-01-01

    Investigation and laboratory experiments with a hydraulic power conversion system for converting forces from a 2.5m diamter float to extract energy from seawaves. The test rig consists of a hydraulic wave simulator and a hydraulic point absorber. The absorber converts the incomming forces...

  11. Impacts of wave energy conversion devices on local wave climate: observations and modelling from the Perth Wave Energy Project

    Science.gov (United States)

    Hoeke, Ron; Hemer, Mark; Contardo, Stephanie; Symonds, Graham; Mcinnes, Kathy

    2016-04-01

    As demonstrated by the Australian Wave Energy Atlas (AWavEA), the southern and western margins of the country possess considerable wave energy resources. The Australia Government has made notable investments in pre-commercial wave energy developments in these areas, however little is known about how this technology may impact local wave climate and subsequently affect neighbouring coastal environments, e.g. altering sediment transport, causing shoreline erosion or accretion. In this study, a network of in-situ wave measurement devices have been deployed surrounding the 3 wave energy converters of the Carnegie Wave Energy Limited's Perth Wave Energy Project. This data is being used to develop, calibrate and validate numerical simulations of the project site. Early stage results will be presented and potential simulation strategies for scaling-up the findings to larger arrays of wave energy converters will be discussed. The intended project outcomes are to establish zones of impact defined in terms of changes in local wave energy spectra and to initiate best practice guidelines for the establishment of wave energy conversion sites.

  12. Spectrum of classes of point emitters of electromagnetic wave fields.

    Science.gov (United States)

    Castañeda, Román

    2016-09-01

    The spectrum of classes of point emitters has been introduced as a numerical tool suitable for the design, analysis, and synthesis of non-paraxial optical fields in arbitrary states of spatial coherence. In this paper, the polarization state of planar electromagnetic wave fields is included in the spectrum of classes, thus increasing its modeling capabilities. In this context, optical processing is realized as a filtering on the spectrum of classes of point emitters, performed by the complex degree of spatial coherence and the two-point correlation of polarization, which could be implemented dynamically by using programmable optical devices.

  13. Excitation Forces on Point Absorbers Exposed to High Order Non-linear Waves

    DEFF Research Database (Denmark)

    Viuff, Thomas Hansen; Andersen, Morten Thøtt; Kramer, Morten

    2013-01-01

    of proper methods to calculate design pressure distributions has led to structural failures such as buckling in the shells in wave energy prototypes. As a step towards understanding the complex loading from high order non-linear waves, this paper presents a practical approach to estimate wave excitation...... forces accounting for both non-linearity and diffraction effects. The method is validated by laboratory experiments using a hemispherical point absorber with a 6-axis force transducer, but the technique is believed to be applicable for most types of submerged or semi-submerged floating devices...

  14. Assessment of wave energy resources in Hawaii

    Energy Technology Data Exchange (ETDEWEB)

    Stopa, Justin E.; Cheung, Kwok Fai [Department of Ocean and Resources Engineering, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Chen, Yi-Leng [Department of Meteorology, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)

    2011-02-15

    Hawaii is subject to direct approach of swells from distant storms as well as seas generated by trade winds passing through the islands. The archipelago creates a localized weather system that modifies the wave energy resources from the far field. We implement a nested computational grid along the major Hawaiian Islands in the global WaveWatch3 (WW3) model and utilize the Weather Research and Forecast (WRF) model to provide high-resolution mesoscale wind forcing over the Hawaii region. Two hindcast case studies representative of the year-round conditions provide a quantitative assessment of the regional wind and wave patterns as well as the wave energy resources along the Hawaiian Island chain. These events of approximately two weeks each have a range of wind speeds, ground swells, and wind waves for validation of the model system with satellite and buoy measurements. The results demonstrate the wave energy potential in Hawaii waters. While the episodic swell events have enormous power reaching 60 kW/m, the wind waves, augmented by the local weather, provide a consistent energy resource of 15-25 kW/m throughout the year. (author)

  15. Analysis of Waves in the Near-Field of Wave Energy Converter Arrays through Stereo Video

    Science.gov (United States)

    Black, C.; Haller, M. C.

    2013-12-01

    Oregon State University conducted a series of laboratory experiments to measure and quantify the near-field wave effects caused within arrays of 3 and 5 Wave Energy Converters (WEC). As the waves and WECs interact, significant scattering and radiation occurs increasing/decreasing the wave heights as well as changing the direction the wave is traveling. These effects may vary based on the number of WECs within an array and their respective locations. The findings of this analysis will assist in selecting the WEC farm location and in improving WEC design. Analyzing the near-field waves will help determine the relative importance of absorption, scattering, and radiation as a function of the incident wave conditions and device performance. The WEC mooring system design specifications may also be impacted if the wave heights in the near-field are greater than expected. It is imperative to fully understand the near-field waves before full-scale WEC farms can be installed. Columbia Power Technologies' Manta served as the test WEC prototype on a 1 to 33 scale. Twenty-three wave gages measured the wave heights in both regular and real sea conditions at locations surrounding and within the WEC arrays. While these gages give a good overall picture of the water elevation behavior, it is difficult to resolve the complicated wave field within the WEC array using point gages. Here stereo video techniques are applied to extract the 3D water surface elevations at high resolution in order to reconstruct the multi-directional wave field in the near-field of the WEC array. The video derived wave information will also be compared against the wave gage data.

  16. Clustering of cycloidal wave energy converters

    Science.gov (United States)

    Siegel, Stefan G.

    2016-03-29

    A wave energy conversion system uses a pair of wave energy converters (WECs) on respective active mountings on a floating platform, so that the separation of the WECs from each other or from a central WEC can be actively adjusted according to the wavelength of incident waves. The adjustable separation facilitates operation of the system to cancel reactive forces, which may be generated during wave energy conversion. Modules on which such pairs of WECs are mounted can be assembled with one or more central WECs to form large clusters in which reactive forces and torques can be made to cancel. WECs of different sizes can be employed to facilitate cancelation of reactive forces and torques.

  17. Probabilistic Forecasting of the Wave Energy Flux

    DEFF Research Database (Denmark)

    Pinson, Pierre; Reikard, G.; Bidlot, J.-R.

    2012-01-01

    markets. A methodology for the probabilistic forecasting of the wave energy flux is introduced, based on a log-Normal assumption for the shape of predictive densities. It uses meteorological forecasts (from the European Centre for Medium-range Weather Forecasts – ECMWF) and local wave measurements......Wave energy will certainly have a significant role to play in the deployment of renewable energy generation capacities. As with wind and solar, probabilistic forecasts of wave power over horizons of a few hours to a few days are required for power system operation as well as trading in electricity...... as input. The parameters of the models involved are adaptively and recursively estimated. The methodology is evaluated for 13 locations around North-America over a period of 15months. The issued probabilistic forecasts substantially outperform the various benchmarks considered, with improvements between 6...

  18. Parametric Study of Two-Body Floating-Point Wave Absorber

    Institute of Scientific and Technical Information of China (English)

    Atena Amiri; Roozbeh Panahi; Soheil Radfar

    2016-01-01

    In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber (FPA) with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter’s efficiency when considering specific conditions.

  19. Energy density and energy flow of magnetoplasmonic waves on graphene

    Science.gov (United States)

    Moradi, Afshin

    2017-03-01

    By means the linearized magnetohydrodynamic theory, expressions for energy density and energy flow are derived for the p-polarized surface magnetoplasmon polaritons on graphene in the Voigt configuration, where a static magnetic field is normal to the graphene surface. Numerical results show that the external magnetic field has significant impact on the energy density and energy transport velocity of magnetoplasmon waves in the long-wavelength region, while total power flow vary only weakly with magnetostatic field. The velocity of energy propagation is proved to be identical with group velocity of the surface waves.

  20. Wave Induced Loads on the LEANCON Wave Energy Converter

    DEFF Research Database (Denmark)

    Frigaard, Peter; Kofoed, Jens Peter; Beserra, Eliab Ricarte

    This report is a product of the co-operation agreement between Aalborg University and LEANCON (by Kurt Due Rasmussen) on the evaluation and development of the LEANCON wave energy converter (WEC). The work reported here has focused on evaluation of the wave induced loads on the device, based...... on a desktop study based on available literature, supplemented by laboratory testing of models of the WEC provided by LEANCON. LEANCON, represented by Kurt Due Rasmussen, has been heavily involved in the testing of the device, including the instrumentation, model setup and execution of the tests...... in the laboratory, all under the supervision of the personnel of the Wave Energy Research Group at Department of Civil Engineering, Aalborg University....

  1. Irreversible Behaviour and Collapse of Wave Packets in a Quantum System with Point Interactions

    CERN Document Server

    Guarneri, Italo

    2011-01-01

    A system of a particle and a harmonic oscillator, which have pure point spectrum if uncoupled, is known to acquire absolutely continuous spectrum when the particle and the oscillator are coupled by a sufficiently strong point interaction. Here the simple dynamical mechanism underlying this phenomenon is exposed. The energy of the oscillator is proven to exponentially diverge in time, while the spatial probability distribution of the particle collapses into a delta function in the interaction point. On account of this result, a generalized model with many oscillators which interact with the particle at different points is argued to provide a formal model for approximate measurement of position, and collapse of wave packets.

  2. Irreversible behaviour and collapse of wave packets in a quantum system with point interactions

    Energy Technology Data Exchange (ETDEWEB)

    Guarneri, Italo [Center for Nonlinear and Complex Systems, Universita dell' Insubria, via Valleggio 11, I-22100 Como (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, via Bassi 6, I-27100 Pavia (Italy)

    2011-12-02

    A system of a particle and a harmonic oscillator, which have pure point spectra if uncoupled, is known to acquire an absolutely continuous spectrum when they are coupled by a sufficiently strong point interaction. Here, the dynamical mechanism underlying this spectral phenomenon is exposed. The energy of the oscillator is proven to exponentially diverge in time, while the spatial probability distribution of the particle collapses into a {delta}-function at the interaction point. On account of this result, a generalized model with many oscillators which interact with the particle at different points is argued to provide a formal model for the approximate measurement of position and collapse of wave packets. (paper)

  3. Aquabuoy Wave Energy Converter

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Margheritini, Lucia; Frigaard, Peter

    The work reported here is part of the contract agreement between the Finavera Renewables Ocean Energy Ltd. and the Department of Civil Engineering Hydraulics and Coastal Engineering Laboratory to instrument a model in scale 1:10 to prototype of the AquaBuOY (AB) wave energy converter and to analyse...

  4. Energy-Momentum Distribution of Gravitational Waves

    Institute of Scientific and Technical Information of China (English)

    M. Sharif; Kanwal Nazir

    2008-01-01

    This paper has been addressed to the well-known problem of energy in gravitational waves.We have investigated the energy of cylindrical gravitational waves in the context of General Relativity and teleparallel theory of gravity.For this purpose,the prescriptions of Einstein,Landau-Lifshitz,Bergmann-Thomson,and Moller are used in both the theories.It is shown that these energy-momentum complexes do not provide equivalent results in the two theories.However,these turn out to be constant for all the prescriptions except Moller in both the theories at large distances.

  5. Whistler Wave Energy Flow in the Plasmasphere

    Science.gov (United States)

    Kletzing, Craig; Santolik, Ondrej; Kurth, William; Hospodarsky, George; Christopher, Ivar; Bounds, Scott

    2016-07-01

    The measured wave properties of plasmaspheric hiss are important to constrain models of the generation of hiss as well as its propagation and amplification. For example, the generation mechanism for plasmaspheric hiss has been suggested to come from one of three possible mechanisms: 1) local generation and amplification, 2) whistlers from lightning, and 3) chorus emissions which have refracted into the plasmasphere. The latter two mechanisms are external sources which produce an incoherent hiss signature as the original waves mix in a stochastic manner, propagating in both directions along the background magnetic field. In contrast, local generation of plasmaspheric hiss within the plasmasphere should produce a signature of waves propagating away from the source region. For all three mechanisms scattering of energetic particles into the loss cone transfers some energy from the particles to the waves. By examining the statistical characteristics of the Poynting flux of plasmaspheric hiss, we can determine the properties of wave energy flow in the plasmasphere. We report on the statistics of observations from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) Waves instrument on the Van Allen Probes for periods when the spacecraft is inside the plasmasphere. We find that the Poynting flux associated with plasmaspheric hiss has distinct and unexpected radial structure which shows that there can be significant energy flow towards the magnetic equator. We show the properties of this electromagnetic energy flow as a function of position and frequency.

  6. Design of full scale wave simulator for testing Power Take Off systems for wave energy converters

    DEFF Research Database (Denmark)

    Pedersen, H. C.; Hansen, R. H.; Hansen, Anders Hedegaard

    2016-01-01

    For wave energy to become a major future contributor of renewable energy it is a requirement that the efficiency and reliability of the Power Take-Off (PTO) systems is significantly improved. However, the cost of installing and testing PTO-systems at sea is very high. The focus of the current paper...... is therefore on the design and commissioning of a full scale wave simulator for testing PTO-systems for point absorbers. The challenge is to be able to design a system, which mimics the behavior of a wave when interacting with a given PTO-system – especially when considering discrete type PTO......-systems. The paper presents the designed system, including the major design considerations. A model of the complete system is presented and controllers for the system are developed. These enable the system to emulate the wave behavior and the wave–float interaction. Finally both simulation and experimental results...

  7. Zero point energy of polyhedral water clusters.

    Science.gov (United States)

    Anick, David J

    2005-06-30

    Polyhedral water clusters (PWCs) are cage-like (H2O)n clusters where every O participates in exactly three H bonds. For a database of 83 PWCs, 8 zero point energy (ZPE) was calculated at the B3LYP/6-311++G** level. ZPE correlates negatively with electronic energy (E0): each increase of 1 kcal/mol in E0 corresponds to a decrease of about 0.11 kcal/mol in ZPE. For each n, a set of four connectivity parameters accounts for 98% or more of the variance in ZPE. Linear regression of ZPE against n and this set gives an RMS error of 0.13 kcal/mol. The contributions to ZPE from stretch modes only (ZPE(S)) and from torsional modes only (ZPE(T)) also correlate strongly with E0 and with each other.

  8. Electromagnetic wave energy conversion research

    Science.gov (United States)

    Bailey, R. L.; Callahan, P. S.

    1975-01-01

    Known electromagnetic wave absorbing structures found in nature were first studied for clues of how one might later design large area man-made radiant-electric converters. This led to the study of the electro-optics of insect dielectric antennae. Insights were achieved into how these antennae probably operate in the infrared 7-14um range. EWEC theoretical models and relevant cases were concisely formulated and justified for metal and dielectric absorber materials. Finding the electromagnetic field solutions to these models is a problem not yet solved. A rough estimate of losses in metal, solid dielectric, and hollow dielectric waveguides indicates future radiant-electric EWEC research should aim toward dielectric materials for maximum conversion efficiency. It was also found that the absorber bandwidth is a theoretical limitation on radiant-electric conversion efficiency. Ideally, the absorbers' wavelength would be centered on the irradiating spectrum and have the same bandwith as the irradiating wave. The EWEC concept appears to have a valid scientific basis, but considerable more research is needed before it is thoroughly understood, especially for the complex randomly polarized, wide band, phase incoherent spectrum of the sun. Specific recommended research areas are identified.

  9. Air Turbines for Wave Energy Conversion

    Directory of Open Access Journals (Sweden)

    Manabu Takao

    2012-01-01

    Full Text Available This paper describes the present status of the art on air turbines, which could be used for wave energy conversion. The air turbines included in the paper are as follows: Wells type turbines, impulse turbines, radial turbines, cross-flow turbine, and Savonius turbine. The overall performances of the turbines under irregular wave conditions, which typically occur in the sea, have been compared by numerical simulation and sea trial. As a result, under irregular wave conditions it is found that the running and starting characteristics of the impulse type turbines could be superior to those of the Wells turbine. Moreover, as the current challenge on turbine technology, the authors explain a twin-impulse turbine topology for wave energy conversion.

  10. Conversion of zero point energy into high-energy photons

    Energy Technology Data Exchange (ETDEWEB)

    Ivlev, B. I. [Universidad Autonoma de San Luis Potosi, Instituto de Fisica, Av. Manuel Nava No. 6, Zona Universitaria, 78290 San Luis Potosi, SLP (Mexico)

    2016-11-01

    An unusual phenomenon, observed in experiments is studied. X-ray laser bursts of keV energy are emitted from a metal where long-living states, resulting in population inversion, are totally unexpected. Anomalous electron-photon states are revealed to be formed inside the metal. These states are associated with narrow, 10{sup -11} cm, potential well created by the local reduction of zero point electromagnetic energy. In contrast to analogous van der Waals potential well, leading to attraction of two hydrogen atoms, the depth of the anomalous well is on the order of 1 MeV. The states in that well are long-living which results in population inversion and subsequent laser generation observed. The X-ray emission, occurring in transitions to lower levels, is due to the conversion of zero point electromagnetic energy. (Author)

  11. Fundamental formulae for wave-energy conversion.

    Science.gov (United States)

    Falnes, Johannes; Kurniawan, Adi

    2015-03-01

    The time-average wave power that is absorbed from an incident wave by means of a wave-energy conversion (WEC) unit, or by an array of WEC units-i.e. oscillating immersed bodies and/or oscillating water columns (OWCs)-may be mathematically expressed in terms of the WEC units' complex oscillation amplitudes, or in terms of the generated outgoing (diffracted plus radiated) waves, or alternatively, in terms of the radiated waves alone. Following recent controversy, the corresponding three optional expressions are derived, compared and discussed in this paper. They all provide the correct time-average absorbed power. However, only the first-mentioned expression is applicable to quantify the instantaneous absorbed wave power and the associated reactive power. In this connection, new formulae are derived that relate the 'added-mass' matrix, as well as a couple of additional reactive radiation-parameter matrices, to the difference between kinetic energy and potential energy in the water surrounding the immersed oscillating WEC array. Further, a complex collective oscillation amplitude is introduced, which makes it possible to derive, by a very simple algebraic method, various simple expressions for the maximum time-average wave power that may be absorbed by the WEC array. The real-valued time-average absorbed power is illustrated as an axisymmetric paraboloid defined on the complex collective-amplitude plane. This is a simple illustration of the so-called 'fundamental theorem for wave power'. Finally, the paper also presents a new derivation that extends a recently published result on the direction-average maximum absorbed wave power to cases where the WEC array's radiation damping matrix may be singular and where the WEC array may contain OWCs in addition to oscillating bodies.

  12. Wave Energy Assessment and Performance Estimation of State of the Art Wave Energy Converters in Italian Hotspots

    Directory of Open Access Journals (Sweden)

    Valentina Vannucchi

    2016-12-01

    Full Text Available This paper presents an assessment of offshore wave energy potential at the scale of the whole Mediterranean Sea. The offshore wave data were propagated, by means of numerical modeling, toward four Italian coastal areas, namely stretches of coast of Tuscany, Liguria, Sardinia and Sicily. For each area, the wave power and the monthly, seasonal and annual variability at water depths of 50 m and 15 m were analyzed and hotspots were located. The results show strong variability of the wave energy potential from point to point of the same area thus highlighting the need for spatially detailed analysis. The higher values of wave energy potential are located in the hotspots of Sardinia and Sicily, at 11.4 kW/m and 9.1 kW/m, respectively. The Tuscany and the Liguria hotspots are characterized, respectively, by 4.7 kW/m and 2.0 kW/m. In order to point out which state of the art WEC is best suited for the Italian areas, the performances of six different state of the art Wave Energy Converters (WECs were evaluated. Finally, a comparison of the performances of each WEC in the selected Italian sites and in some European (EU oceanic sites was conducted. The energy potential in the most energetic EU oceanic site, among those here investigated, is up to 38-times greater than the potentials in the studied Italian areas but the power output, of the best WEC technology, is no more than nine times greater.

  13. Wave Energy, Lever Operated Pivoting Float LOPF Study

    DEFF Research Database (Denmark)

    Margheritini, Lucia

    University in Denmark. The model size was 60cm W x 90cm L x 21cm H. The 60 cm width pointed towards the wave front. The LOPF buoy is characterized by a simple mechanical design with few moving parts and direct electrical output and it is taut moored to the sea bed, so all forces are referenced to the seabed......The fully instrumented Resen Waves Lever Operated Pivoting Float LOPF wave energy buoy model has gone through the first stage of testing in regular waves in scale 1:25 of the North Sea wave conditions, in the 3D deep wave basin at the Hydraulic and Coastal Engineering Laboratory of Aalborg...... for maximum energy output in regular as well as irregular waves. During storms the buoy pivots and streamlines itself to minimize loads on the mooring line. A conservative estimate shows that a full scale system for North Sea conditions has a float size width of 15 m that will, with 60% generator efficiency...

  14. Reliability assessment of wave Energy devices

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kramer, Morten; Kofoed, Jens Peter

    2014-01-01

    Energy from waves may play a key role in sustainable electricity production in the future. Optimal reliability levels for components used for Wave Energy Devices (WEDs) need to be defined to be able to decrease their cost of electricity. Optimal reliability levels can be found using probabilistic...... methods. Extreme loads during normal operation, but also extreme loads simultaneous with failure of mechanical and electrical components as well as the control system, are of importance for WEDs. Furthermore, fatigue loading needs to be assessed. This paper focus on the Wavestar prototype which is located...

  15. Experimental Validation of aWave Energy Converter Array Hydrodynamics Tool

    DEFF Research Database (Denmark)

    Ruiz, Pau Mercadé; Ferri, Francesco; Kofoed, Jens Peter

    2017-01-01

    This paper uses experimental data to validate a wave energy converter (WEC) array hydrodynamics tool developed within the context of linearized potential flow theory. To this end, wave forces and power absorption by an array of five-point absorber WECs in monochromatic and panchromatic waves were...

  16. Ocean Wave Energy Harvesting Devices

    Science.gov (United States)

    2008-01-01

    limited life due to size-weight constraints - Market opportunity exists with Navy for AUV, UUV applications +Gateway buoy L Energy harvester TDY...and commercial markets . 9.4 Scientific and Technical Results and Accomplishments Results of the effort in relation to program objectives 1. A device...C:l 2 .- 1 cc.c. 4-’I U))( 0o 00 LD, o... ....4 - ... . .... . . .. .. . .. . ; ..][ o V n) 0 L-4-’ Ncco 4-0 ) UU -- a),a U) 1X1 ~ cu a0 cU w4 0 C

  17. Sunspot waves and flare energy release

    CERN Document Server

    Sych, R; Altyntsev, A; Dudík, J; Kashapova, L

    2014-01-01

    We address a possibility of the flare process initiation and further maintenance of its energy release due to a transformation of sunspot longitudinal waves into transverse magnetic loop oscillations with initiation of reconnection. This leads to heating maintaining after the energy release peak and formation of a flat stage on the X-ray profile. We applied the time-distance plots and pixel wavelet filtration (PWF) methods to obtain spatio-temporal distribution of wave power variations in SDO/AIA data. To find magnetic waveguides, we used magnetic field extrapolation of SDO/HMI magnetograms. The propagation velocity of wave fronts was measured from their spatial locations at specific times. In correlation curves of the 17 GHz (NoRH) radio emission we found a monotonous energy amplification of 3-min waves in the sunspot umbra before the 2012 June 7 flare. This dynamics agrees with an increase in the wave-train length in coronal loops (SDO/AIA, 171 {\\AA}) reaching the maximum 30 minutes prior to the flare onset...

  18. Discretizing singular point sources in hyperbolic wave propagation problems

    Science.gov (United States)

    Petersson, N. Anders; O'Reilly, Ossian; Sjögreen, Björn; Bydlon, Samuel

    2016-09-01

    We develop high order accurate source discretizations for hyperbolic wave propagation problems in first order formulation that are discretized by finite difference schemes. By studying the Fourier series expansions of the source discretization and the finite difference operator, we derive sufficient conditions for achieving design accuracy in the numerical solution. Only half of the conditions in Fourier space can be satisfied through moment conditions on the source discretization, and we develop smoothness conditions for satisfying the remaining accuracy conditions. The resulting source discretization has compact support in physical space, and is spread over as many grid points as the number of moment and smoothness conditions. In numerical experiments we demonstrate high order of accuracy in the numerical solution of the 1-D advection equation (both in the interior and near a boundary), the 3-D elastic wave equation, and the 3-D linearized Euler equations.

  19. Wave-Structure Interactions on Point Absorbers - an experimental study

    DEFF Research Database (Denmark)

    Jakobsen, Morten Møller

    used in the case studies is a pitching point absorber (Wavestar). The central part of the thesis deals with the challenges, choices, and experi- ences gained during the Ph.D. The more in-depth technical details and results are presented in peer-reviewed publications and technical reports. The chal...... models. Using a modification by Faltinsen to take into account the relative motion of the device, the contributions from drag, excitation and body motion are determined. 2: Determining the peak pressure on the surface on the device during extreme events and in freak conditions. A great deal of work has...... been done to determine peak pressures on mono-piles worldwide, but only very little on spherical structures. In order to shed more light on the wave induced loads on a hemisphere the peak pressures are measured with the traditional drop test and during impact of so-called freak waves. 3: Implementation...

  20. Underwater noise from a wave energy converter

    DEFF Research Database (Denmark)

    Tougaard, Jakob

    A recent addition to the anthropogenic sources of underwater noise is offshore wave energy converters. Underwater noise was recorded from the Wavestar wave energy converter located at Hastholm, Denmark (57°7.73´N, 8°37.23´E). The Wavestar is a full-scale test and demonstration converter...... in full operation and start and stop of the converter. Median broad band (10 Hz – 20 kHz) sound pressure level (Leq) was 123 dB re. 1 Pa, irrespective of status of the wave energy converter (stopped, running or starting/stopping). The most pronounced peak in the third-octave spectrum was in the 160 Hz...... significant noise above ambient could be detected above the 250 Hz band. The absolute increase in noise above ambient was very small. L50 third-octave levels in the four bands with the converter running were thus only 1-2 dB above ambient L50 levels. The noise recorded 25 m from the wave energy converter...

  1. Systems and methods for wave energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    MacDonald, Daniel G.; Cantara, Justin; Nathan, Craig; Lopes, Amy M.; Green, Brandon E.

    2017-02-28

    Systems for wave energy conversion that have components that can survive the harsh marine environment and that can be attached to fixed structures, such as a pier, and having the ability to naturally adjust for tidal height and methods for their use are presented.

  2. Wave energy extraction using decommisioned ships

    DEFF Research Database (Denmark)

    Mansour, A.E.; Pedersen, Preben Terndrup; Paik, J.K.

    2013-01-01

    to scrap naval vessels in 2002 was $33.4 million. Now apparently the Navy sinks naval vessels by bombs and torpedos. Scrapping can cause pollution, health hazards, accidents and threat to the ecosystem. Can a “polluting” ship about to be scrapped be used to generate clean wave energy? Maybe! It is possible...

  3. Discrete control of resonant wave energy devices.

    Science.gov (United States)

    Clément, A H; Babarit, A

    2012-01-28

    Aiming at amplifying the energy productive motion of wave energy converters (WECs) in response to irregular sea waves, the strategies of discrete control presented here feature some major advantages over continuous control, which is known to require, for optimal operation, a bidirectional power take-off able to re-inject energy into the WEC system during parts of the oscillation cycles. Three different discrete control strategies are described: latching control, declutching control and the combination of both, which we term latched-operating-declutched control. It is shown that any of these methods can be applied with great benefit, not only to mono-resonant WEC oscillators, but also to bi-resonant and multi-resonant systems. For some of these applications, it is shown how these three discrete control strategies can be optimally defined, either by analytical solution for regular waves, or numerically, by applying the optimal command theory in irregular waves. Applied to a model of a seven degree-of-freedom system (the SEAREV WEC) to estimate its annual production on several production sites, the most efficient of these discrete control strategies was shown to double the energy production, regardless of the resource level of the site, which may be considered as a real breakthrough, rather than a marginal improvement.

  4. Inventing a Better Way to Capture the Energy of Waves

    Energy Technology Data Exchange (ETDEWEB)

    2016-06-01

    NREL's ocean energy research team's efforts to develop more robust and cost-effective wave energy converters have yielded a record of invention titled, 'Wave Energy Conversion Devices with Actuated Geometry.' This innovative wave device features a wave converter with controlled geometry that increases energy capture and prevents large waves from overloading the generator. The invention's control system actuates flaps that open and close depending on wave conditions. Better control of the wave forces acting on wave energy conversion devices provides a solution to one of wave energy's biggest challenges -- and could cut the cost of wave energy in half.

  5. Reliability Assessment of Wave Energy Devices

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kramer, Morten; Kofoed, Jens Peter;

    2012-01-01

    This paper focuses on reliability assessment of Wave Energy Device (WED) substructures with respect to fatigue loading. Failure due to fatigue is an important failure mode of most offshore structures. The focus of the fatigue reliability assessment is in this paper on welded details in steel...... substructures. The methodology is illustrated using the Wavestar prototype located at Hanstholm (DK) as a case study. The stochastic model presented can be used for reliability assessment and for calibration of Fatigue Design Factors (FDF) of wave power plant substructures. The fatigue life is modeled using...

  6. Wind and Wave Driven Nearshore Circulation at Cape Hatteras Point

    Science.gov (United States)

    Kumar, N.; Voulgaris, G.; Warner, J. C.; List, J. H.

    2012-12-01

    We have used a measurement and modeling approach to identify hydrodynamic processes responsible for alongshore transport of sediment that can support the maintenance of Diamond Shoals, NC, a large inner-shelf sedimentary convergent feature. As a part of Carolina Coastal Change Processes project, a one month field experiment was conducted around Cape Hatteras point during February, 2010. The instrumentation consisted of 15 acoustic current meters (measuring pressure and velocity profile) deployed in water depths varying from 3-10m and a very high frequency (VHF) beam forming radar system providing surface waves and currents with a resolution of 150 m and a spatial coverage of 10-15 km2. Analysis of field observation suggests that wind-driven circulation and littoral current dominate surf zone and inner shelf processes at least at an order higher than tidally rectified flows. However, the data analysis identified that relevant processes like non-linear advective acceleration, pressure gradient and vortex-force (due to interaction between wave-induced drift and mean flow vorticity), may be significant, but were not assessed accurately due to instrument location and accuracy. To obtain a deeper physical understanding of the hydrodynamics in this study-site, we applied a three-dimensional Coupled-Ocean-Atmosphere-Wave_Sediment-Transport (COAWST) numerical model. The COAWST modeling system is comprised of nested, coupled, three-dimensional ocean-circulation model (ROMS) and wave propagation model (SWAN), configured for the study site to simulate wave height, direction, period and mean current velocities (both Eulerian and Lagrangian). The nesting follows a two-way grid refinement process for the circulation module, and one-way for the wave model. The coarsest parent grid resolved processes on the spatial and temporal scales of mid-shelf to inner-shelf, and subsequent child grids evolved at inner-shelf and surf zone scales. Preliminary results show that the model

  7. Wave-particle and wave-wave interactions in hot plasmas: a French historical point of view

    Science.gov (United States)

    Laval, Guy; Pesme, Denis; Adam, Jean-Claude

    2016-11-01

    The first researches on nuclear fusion for energy applications marked the entrance of hot plasmas into the laboratory. It became necessary to understand the behavior of such plasmas and to learn how to manipulate them. Theoreticians and experimentalists, building on the foundations of empirical laws, had to construct this new plasma physics from first principles and to explain the results of more and more complicated experiments. Along this line, two important topics emerged: wave-particle and wave-wave interactions. Here, their history is recalled as it has been lived by a French team from the end of the sixties to the beginning of the twenty-first century.

  8. Dynamics of Nearshore Sand Bars and Infra-gravity Waves: The Optimal Theory Point of View

    Science.gov (United States)

    Bouchette, F.; Mohammadi, B.

    2016-12-01

    It is well known that the dynamics of near-shore sand bars are partly controlled by the features (location of nodes, amplitude, length, period) of the so-called infra-gravity waves. Reciprocally, changes in the location, size and shape of near-shore sand bars can control wave/wave interactions which in their turn alter the infra-gravity content of the near-shore wave energy spectrum. The coupling infra-gravity / near-shore bar is thus definitely two ways. Regarding numerical modelling, several approaches have already been considered to analyze such coupled dynamics. Most of them are based on the following strategy: 1) define an energy spectrum including infra-gravity, 2) tentatively compute the radiation stresses driven by this energy spectrum, 3) compute sediment transport and changes in the seabottom elevation including sand bars, 4) loop on the computation of infra-gravity taking into account the morphological changes. In this work, we consider an alternative approach named Nearshore Optimal Theory, which is a kind of breakdown point of view for the modeling of near-shore hydro-morphodynamics and wave/ wave/ seabottom interactions. Optimal theory applied to near-shore hydro-morphodynamics arose with the design of solid coastal defense structures by shape optimization methods, and is being now extended in order to model dynamics of any near-shore system combining waves and sand. The basics are the following: the near-shore system state is through a functional J representative of the energy of the system in some way. This J is computed from a model embedding the physics to be studied only (here hydrodynamics forced by simple infra-gravity). Then the paradigm is to say that the system will evolve so that the energy J tends to minimize. No really matter the complexity of wave propagation nor wave/bottom interactions. As soon as J embeds the physics to be explored, the method does not require a comprehensive modeling. Near-shore Optimal Theory has already given

  9. Wave energy, lever operated pivoting float LOPF study

    Energy Technology Data Exchange (ETDEWEB)

    Margheritini, L.

    2012-11-01

    The fully instrumented Resen Waves Lever Operated Pivoting Float LOPF wave energy buoy model has gone through the first stage of testing in regular waves in scale 1:25 of the North Sea wave conditions, in the 3D deep wave basin at the Hydraulic and Coastal Engineering Laboratory of Aalborg University in Denmark. The model size was 60cm W x 90cm L x 21cm H. The 60 cm width pointed towards the wave front. The LOPF buoy is characterized by a simple mechanical design with few moving parts and direct electrical output and it is taut moored to the sea bed, so all forces are referenced to the seabed for maximum energy output in regular as well as irregular waves. During storms the buoy pivots and streamlines itself to minimize loads on the mooring line. A conservative estimate shows that a full scale system for North Sea conditions has a float size width of 15 m that will, with 60% generator efficiency, produce 610 MWh/y (609.497 kWh/y) with an average power output of 69.6 kW, which requires a generator capacity of 700 kW. It is expected the generator efficiency can be increased to 90% in the future. More specific calculations (from EnergiNet) show that with one generator of 695 kW the expected power production is 585 MWh/y; with a generator of 250 kW and 100 kW, the expected power production is 481 MWh/y and 182 MWh/y respectively. In addition there are several areas for future improvements for increased power production. (Author)

  10. A Three-Point Method for Separating Incident and Reflected Waves over A Sloping Bed

    Institute of Scientific and Technical Information of China (English)

    CHANG Hsien-Kuo

    2002-01-01

    This study presents a three-point method for separating incident and reflected waves to explain normally incident waves' propagating over a sloping bed. Linear wave shoaling is used to determine changes in wave amplitude and phase in response to variations of bathymetry. The wave reflection coefficient and incident amplitude are estimated from wave heights measured at three fixed wave gauges with unequal spacing. Sensitivity analysis demonstrates that the proposed method can predict the reflection and amplitude of waves over a sloping bed more accurately than the two-point method.

  11. Wave energy transmission apparatus for high-temperature environments

    Science.gov (United States)

    Buckley, John D. (Inventor); Edwards, William C. (Inventor); Kelliher, Warren C. (Inventor); Carlberg, Ingrid A. (Inventor)

    2010-01-01

    A wave energy transmission apparatus has a conduit made from a refractory oxide. A transparent, refractory ceramic window is coupled to the conduit. Wave energy passing through the window enters the conduit.

  12. Underwater Noise Modelling of Wave Energy Devices

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2009-07-01

    Future large-scale implementation of wave energy converts (WECs) will introduce an anthropogenic activity in the ocean which may contribute to underwater noise. The Ocean houses several marine species with acoustic sensibility; consequently the potential impact of the underwater noise needs to be addressed. At present, there are no acoustic impact studies based on acquired data. The WEAM project (Wave Energy Acoustic Monitoring) aims at developing an underwater noise monitoring plan for WECs. The development of an acoustic monitoring plan must consider the sound propagation in the ocean, identify noise sources, understand the operational characteristics and select adequate instrumentation. Any monitoring strategy must involve in-situ measurements. However, the vast distances which sound travels within the ocean, can make in-situ measurements covering the entire area of interest, impracticable. This difficulty can be partially overcome through acoustic numerical modelling. This paper presents a synthetic study, on the application of acoustic forward modelling and the evaluation of the impact of noise produced by wave energy devices on marine mammals using criteria based on audiograms of dolphins, or other species. The idea is to illustrate the application of that methodology, and to show to what extent it allows for estimating distances of impacts due to acoustic noise.

  13. Phase Mixing of Alfv\\'en Waves Near a 2D Magnetic Null Point

    CERN Document Server

    McLaughlin, J A

    2014-01-01

    The propagation of linear Alfv\\'en wave pulses in an inhomogeneous plasma near a 2D coronal null point is investigated. When a uniform plasma density is considered, it is seen that an initially planar Alfv\\'en wavefront remains planar, despite the varying equilibrium Alfv\\'en speed, and that all the wave collects at the separatrices. Thus, in the non-ideal case, these Alfv\\'enic disturbances preferentially dissipate their energy at these locations. For a non-uniform equilibrium density, it is found that the Alfv\\'en wavefront is significantly distorted away from the initially planar geometry, inviting the possibility of dissipation due to phase mixing. Despite this however, we conclude that for the Alfv\\'en wave, current density accumulation and preferential heating still primarily occur at the separatrices, even when an extremely non-uniform density profile is considered.

  14. Phase Mixing of Alfvén Waves Near a 2D Magnetic Null Point

    Indian Academy of Sciences (India)

    J. A. McLaughlin

    2013-09-01

    The propagation of linear Alfvén wave pulses in an inhomogeneous plasma near a 2D coronal null point is investigated. When a uniform plasma density is considered, it is seen that an initially planar Alfvén wavefront remains planar, despite the varying equilibrium Alfvén speed, and that all the wave collects at the separatrices. Thus, in the non-ideal case, these Alfvénic disturbances preferentially dissipate their energy at these locations. For a non-uniform equilibrium density, it is found that the Alfvén wavefront is significantly distorted away from the initially planar geometry, inviting the possibility of dissipation due to phase mixing. Despite this however, we conclude that for the Alfvén wave, current density accumulation and preferential heating still primarily occur at the separatrices, even when an extremely non-uniform density profile is considered.

  15. Worlds Largest Wave Energy Project 2007 in Wales

    DEFF Research Database (Denmark)

    Christensen, Lars; Friis-Madsen, Erik; Kofoed, Jens Peter

    2006-01-01

    a large number of fundamentally different technologies are utilised to harvest wave energy. The Wave Dragon belongs to the wave overtopping class of converters and the paper describes the fundamentals and the technical solutions used in this wave energy converter. An offshore floating WEC like the Wave......This paper introduces world largest wave energy project being developed in Wales and based on one of the leading wave energy technologies. The background for the development of wave energy, the total resource ands its distribution around the world is described. In contrast to wind energy turbines...... Dragon has to be scaled in accordance with the wave climate at the deployment site, which makes the Welch demonstrator device the worlds largest WEC so far with a total width of 300 meters. The project budget, the construction methods and the deployment site are also given....

  16. Coordinated Control of Wave Energy Converters Subject to Motion Constraints

    OpenAIRE

    2016-01-01

    In this paper, a generic coordinated control method for wave energy converters is proposed, and the constraints on motion amplitudes and the hydrodynamic interaction between converters are considered. The objective of the control problem is to maximize the energy converted from ocean waves, and this is achieved by coordinating the power take-off (PTO) damping of each wave energy converter in the frequency domain in each sea state. In a case study, a wave energy farm consisting of four convert...

  17. Wave Energy Research, Testing and Demonstration Center

    Energy Technology Data Exchange (ETDEWEB)

    Batten, Belinda [Oregon State Univ., Corvallis, OR (United States)

    2014-09-30

    The purpose of this project was to build upon the research, development and testing experience of the Northwest National Marine Renewable Energy Center (NNMREC) to establish a non-grid connected open-ocean testing facility for wave energy converters (WECs) off the coast of Newport, Oregon. The test facility would serve as the first facility of its kind in the continental US with a fully energetic wave resource where WEC technologies could be proven for west coast US markets. The test facility would provide the opportunity for self-contained WEC testing or WEC testing connected via an umbilical cable to a mobile ocean test berth (MOTB). The MOTB would act as a “grid surrogate” measuring energy produced by the WEC and the environmental conditions under which the energy was produced. In order to realize this vision, the ocean site would need to be identified through outreach to community stakeholders, and then regulatory and permitting processes would be undertaken. Part of those processes would require environmental baseline studies and site analysis, including benthic, acoustic and wave resource characterization. The MOTB and its myriad systems would need to be designed and constructed.The first WEC test at the facility with the MOTB was completed within this project with the WET-NZ device in summer 2012. In summer 2013, the MOTB was deployed with load cells on its mooring lines to characterize forces on mooring systems in a variety of sea states. Throughout both testing seasons, studies were done to analyze environmental effects during testing operations. Test protocols and best management practices for open ocean operations were developed. As a result of this project, the non-grid connected fully energetic WEC test facility is operational, and the MOTB system developed provides a portable concept for WEC testing. The permitting process used provides a model for other wave energy projects, especially those in the Pacific Northwest that have similar

  18. Practical performances of MPC for wave energy converters

    DEFF Research Database (Denmark)

    Ferri, Francesco; Tetu, Amelie; Hals, J.

    2016-01-01

    Maximising the efficiency of Wave Energy Converter (WEC) is one of the important tasks toward the exploitation of the wave energy resource. Along with a proper design of the device, an important way to achieve better energy performances is to improve the wave-body interaction by applying an appro...

  19. Experimental Study of the Weptos Wave Energy Converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter; Larsen, Tommy

    2012-01-01

    This paper presents the power performance results of the experimental study of the WEPTOS wave energy converter (WEC). This novel device combines an established and efficient wave energy absorbing mechanism with an adjustable structure that can regulate the amount of incoming wave energy and redu...

  20. EB Frond wave energy converter - phase 2

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    The EB Frond project is a wave energy programme developed by The Engineering Business (EB) from an original idea at Lancaster University. The EB Frond is a wave generator with a collector vane on top of an arm that pivots near the seabed. Phase 1 of the project demonstrated the technical feasibility of the project and provided proof of concept. Phase 2 involved further assesment of the technical and commercial viability of the concept through the development of mathematical and physical modelling methods. The work involved small-scale (1/25th) testing in wave tanks at Newcastle and Lancaster Universities and the development, verification and validation of a time domain mathematical model. The decision by EB to put on hold its renewable generation programme meant that plans to test at an intermediate scale (1/16th), assess different survival strategies in extreme wave conditions, carry out site characterisation for full-scale systems and to produce a robust economic model were not fulfilled. However, the mathematical and physical modelling work was used to develop an economic model for the Frond system. This produced a predicted unit cost of electricity by a pre-commercial 5 MW demonstration farm of about 17 pence/kWh. The report discusses the small-scale testing, test results, mathematical modelling, analysis and interpretation, survivability, the economic model and the development route to full-scale production.

  1. Internal energy relaxation in shock wave structure

    Science.gov (United States)

    Josyula, Eswar; Suchyta, Casimir J.; Boyd, Iain D.; Vedula, Prakash

    2013-12-01

    The Wang Chang-Uhlenbeck (WCU) equation is numerically integrated to characterize the internal structure of Mach 3 and Mach 5 shock waves in a gas with excitation in the internal energy states for the treatment of inelastic collisions. Elastic collisions are modeled with the hard sphere collision model and the transition rates for the inelastic collisions modified appropriately using probabilities based on relative velocities of the colliding particles. The collision integral is evaluated by the conservative discrete ordinate method [F. Tcheremissine, "Solution of the Boltzmann kinetic equation for high-speed flows," Comput. Math. Math. Phys. 46, 315-329 (2006); F. Cheremisin, "Solution of the Wang Chang-Uhlenbeck equation," Dokl. Phys. 47, 487-490 (2002)] developed for the Boltzmann equation. For the treatment of the diatomic molecules, the internal energy modes in the Boltzmann equation are described quantum mechanically given by the WCU equation. As a first step in the treatment of the inelastic collisions by the WCU equation, a two- and three-quantum system is considered to study the effect of the varying of (1) the inelastic cross section and (2) the energy gap between the quantum energy states. An alternative method, the direct simulation Monte Carlo method, is used for the Mach 3 shock wave to ensure the consistency of implementation in the two methods and there is an excellent agreement between the two methods. The results from the WCU implementation showed consistent trends for the Mach 3 and Mach5 standing shock waves simulations. Inelastic contributions change the downstream equilibrium state and allow the flow to transition to the equilibrium state further upstream.

  2. Apparent energy distribution of sea waves

    Institute of Scientific and Technical Information of China (English)

    孙孚; 丁平兴

    1995-01-01

    A concept of apparent energy distribution of sea waves is suggested and named "the outer frequency spectrum" to distinguish it from the frequency spectrum in common sense In line with the concept, a kind of outer spectrum with three parameters in Cauchy’ s form is derived theoretically from the joint distribution of wave periods and heights reached previously by the present authors and the Bretschneider spectrum is rededuced simply in a distinct manner. The foundation of mechanics of the similarity between the frequency spectrum in common sense and the outer one is briefly discussed. In view of the fact that Bretschneider spectrum has a wide application in engineering, the advantages and probability of using the outer spectrum as a common one are also considered.

  3. Forecasting ocean wave energy: A Comparison of the ECMWF wave model with time series methods

    DEFF Research Database (Denmark)

    Reikard, Gordon; Pinson, Pierre; Bidlot, Jean

    2011-01-01

    days. In selecting a method, the forecaster has a choice between physics-based models and statistical techniques. A further idea is to combine both types of models. This paper analyzes the forecasting properties of a well-known physics-based model, the European Center for Medium-Range Weather Forecasts......Recently, the technology has been developed to make wave farms commercially viable. Since electricity is perishable, utilities will be interested in forecasting ocean wave energy. The horizons involved in short-term management of power grids range from as little as a few hours to as long as several...... energy flux. In the initial tests, the ECMWF model and the statistical models are compared directly. The statistical models do better at short horizons, producing more accurate forecasts in the 1–5 h range. The ECMWF model is superior at longer horizons. The convergence point, at which the two methods...

  4. The zero point energy and gravitation

    CERN Document Server

    Culetu, H

    2004-01-01

    A possible connection between the energy W of the vacuum fluctuations of quantum fields and gravity in "empty space" is conjectured in this paper using a natural cutoff of high momenta with the help of the gravitational radius of the vacuum region considered. We found that below some "critical" length $L = 1 mm$ the pressure $sigma$ is one third of the energy density $epsilon$, as for dark matter, but above $1 mm$ the equation of state is $sigma = -(epsilon)$ (dark energy). In the case of a massive field, W does not depend on the mass of the field for $L1 mm$ but for $L1 mm$ it does not depend on the Planck constant. In addition, when the Newton constant tends to zero, W becomes infinite. The energy density is also a function of the volume V of the vacuum region taken into account.

  5. Design guidelines of triboelectric nanogenerator for water wave energy harvesters

    Science.gov (United States)

    Ahmed, Abdelsalam; Hassan, Islam; Jiang, Tao; Youssef, Khalid; Liu, Lian; Hedaya, Mohammad; Abu Yazid, Taher; Zu, Jean; Wang, Zhong Lin

    2017-05-01

    Ocean waves are one of the cleanest and most abundant energy sources on earth, and wave energy has the potential for future power generation. Triboelectric nanogenerator (TENG) technology has recently been proposed as a promising technology to harvest wave energy. In this paper, a theoretical study is performed on a duck-shaped TENG wave harvester recently introduced in our work. To enhance the design of the duck-shaped TENG wave harvester, the mechanical and electrical characteristics of the harvester’s overall structure, as well as its inner configuration, are analyzed, respectively, under different wave conditions, to optimize parameters such as duck radius and mass. Furthermore, a comprehensive hybrid 3D model is introduced to quantify the performance of the TENG wave harvester. Finally, the influence of different TENG parameters is validated by comparing the performance of several existing TENG wave harvesters. This study can be applied as a guideline for enhancing the performance of TENG wave energy harvesters.

  6. Design guidelines of triboelectric nanogenerator for water wave energy harvesters

    KAUST Repository

    Ahmed, Abdelsalam

    2017-04-11

    Ocean waves are one of the cleanest and most abundant energy sources on earth, and wave energy has the potential for future power generation. Triboelectric nanogenerator (TENG) technology has recently been proposed as a promising technology to harvest wave energy. In this paper, a theoretical study is performed on a duck-shaped TENG wave harvester recently introduced in our work. To enhance the design of the duck-shaped TENG wave harvester, the mechanical and electrical characteristics of the harvester\\'s overall structure, as well as its inner configuration, are analyzed, respectively, under different wave conditions, to optimize parameters such as duck radius and mass. Furthermore, a comprehensive hybrid 3D model is introduced to quantify the performance of the TENG wave harvester. Finally, the influence of different TENG parameters is validated by comparing the performance of several existing TENG wave harvesters. This study can be applied as a guideline for enhancing the performance of TENG wave energy harvesters.

  7. Sea wave energy based in nanotechnology

    Energy Technology Data Exchange (ETDEWEB)

    Duque, Carlos

    2010-09-15

    Application on which it turns east document is the recovery of the energy of the sea waves turning it into electricity by means of the combination of nano-piezoelectric and condensing, the system would be seen like a compound floating fabric of million piezoelectric crystals that turn the oscillating movement of the sea into micro-electrical signals that they are added and they left by means cables to the surface where electronics devices classified to the load of condensers, from the electricity is confined and later is invested and synchronize itself with the great national mains.

  8. Magnetohydrodynamic wave propagation from the subphotosphere to the corona in an arcade-shaped magnetic field with a null point

    Science.gov (United States)

    Santamaria, I. C.; Khomenko, E.; Collados, M.

    2015-05-01

    Aims: The aim of this work is to study the energy transport by means of Magnetohydrodynamic (MHD) waves propagating in quiet-Sun magnetic topology from layers below the surface to the corona. Upwardly propagating waves find obstacles, such as the equipartition layer with plasma β = 1, the transition region, and null points, and they get transmitted, converted, reflected, and refracted. Understanding the mechanisms by which MHD waves can reach the corona can give us information about the solar atmosphere and the magnetic structures. Methods: We carried out two-dimensional numerical simulations of wave propagation in a magnetic field structure that consists of two vertical flux tubes with the same polarity separated by an arcade-shaped magnetic field. This configuration contains a null point in the corona, which significantly modifies the behavior of the waves as they pass near it. Results: We describe in detail the wave propagation through the atmosphere under different driving conditions. We also present the spatial distribution of the mean acoustic and magnetic energy fluxes for the cases where these calculations are possible, as well as the spatial distribution of the dominant frequencies in the whole domain. Conclusions: We conclude that the energy reaches the corona preferably along almost vertical magnetic fields, that is, inside the vertical flux tubes. This energy is acoustic in nature. Most of the magnetic energy stays concentrated below the transition region owing to the refraction of the magnetic waves and the continuous conversion of acoustic-like waves into fast magnetic waves in the equipartition layer located in the photosphere where plasma β = 1. However, part of the magnetic energy reaches the low corona when propagating in the region where the arcades are located, but waves are sent back downward into the lower atmosphere at the null-point surroundings. This phenomenon, together with the reflection and refraction of waves in the TR and the lower

  9. The Potential for Wave Energy in the North Sea

    DEFF Research Database (Denmark)

    Sørensen, H. C.; Chozas, Julia Fernandez

    2010-01-01

    The North Sea has not yet been regarded as prime area for wave energy development in Europe except in Denmark, Benelux and Germany. The reason is the relatively low intensity of waves (12-17kW/m) compared to the Atlantic with a wave climate of 24-48kW/m. Further on the design wave load is almost ...

  10. Magnetoacoustic Waves in a Stratified Atmosphere with a Magnetic Null Point

    CERN Document Server

    Tarr, Lucas A; Leake, James

    2016-01-01

    We perform nonlinear MHD simulations to study the propagation of magnetoacoustic waves from the photosphere to the low corona. We focus on a 2D system with a gravitationally stratified atmosphere and three photospheric concentrations of magnetic flux that give rise to a magnetic null point with a magnetic dome topology. We find that a single wavepacket introduced at the lower boundary splits into multiple secondary wavepackets. A portion of the packet refracts towards the null due to the varying Alfv\\'en speed. Waves incident on the equipartition contour surrounding the null, where the sound and Alfv\\'en speeds coincide, partially transmit, reflect, and mode convert between branches of the local dispersion relation. Approximately $15.5\\%$ of the wavepacket's initial energy ($E_{input}$) converges on the null, mostly as a fast magnetoacoustic wave. Conversion is very efficient: $70\\%$ of the energy incident on the null is converted to slow modes propagating away from the null, $7\\%$ leaves as a fast wave, and ...

  11. Hydraulic Evaluation of the Crest Wing Wave Energy Converter

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Antonishen, Michael Patrick

    This report presents the results of an experimental study of the wave energy converting abilities of the Crest Wing wave energy converter (WEC). The Crest Wing is a WEC that uses its movement in matching the shape of an oncoming wave to generate power. Model tests have been performed using a scale...... model (length scale 1:30), provided by WaveEnergyFyn, in regular and irregular wave states that can be found in Assessment of Wave Energy Devices. Best Practice as used in Denmark (Frigaard et al., 2008). The tests were carried out at Dept. of Civil Engineering, Aalborg (Frigaard et al., 2008......). The tests were carried out at Dept. of Civil Engineering, Aalborg University (AAU) in the 3D deep water wave tank. The displacement and force applied to a power take off system, provided by WaveEnergyFyn, were measured and used to calculate total power take off....

  12. The Draukie's Tale: Origin Myth for Wave Energy

    DEFF Research Database (Denmark)

    Watts, Laura

    2017-01-01

    Poem based on ethnographic research with people and places around the European Marine Energy Centre, the world's longest running test site for wave and tide energy, Orkney islands, Scotland.......Poem based on ethnographic research with people and places around the European Marine Energy Centre, the world's longest running test site for wave and tide energy, Orkney islands, Scotland....

  13. Energy Consumption of Wireless Network Access Points

    OpenAIRE

    ANDRADE MORELLI, SEBASTIÁN; RUIZ SANCHEZ, EDUARDO; GRANELL ROMERO, EMILIO; Lloret, Jaime

    2013-01-01

    2nd International Conference on Green Communications and Networking, GreeNets 2012; Gandia; Spain; 25 October 2012 through 26 October 2012 The development of low cost technology based on IEEE 802.11 standard permits to build telecommunication networks at low cost, allowing providing Internet access in rural areas in developing countries. The lack of access to the electrical grid is a problem when the network is being developed in rural areas, so that wireless access points should operate u...

  14. HARDENING FROG POINTS BY EXPLOSIVE ENERGY,

    Science.gov (United States)

    Experiments were made to determine the most efficient method of strain hardening railroad frog points in order to increase their fatigue resistance...Mechanical strain hardening with rolls 40 mm in diameter under a load of 8 tons produced in standard frogs cast from G13L high-manganese steel (AISI...Hadfield steel) a work-hardened surface layer 3-5 mm thick with a hardness of 340 HB. In other experiments, the frogs were hardened by exploding a

  15. Modeling the Buoyancy System of a Wave Energy Power Plant

    DEFF Research Database (Denmark)

    Pedersen, Tom S.; Nielsen, Kirsten M.

    2009-01-01

    A nonlinear dynamic model of the buoyancy system in a wave energy power plant is presented. The plant ("Wave Dragon") is a floating device using the potential energy in overtopping waves to produce power. A water reservoir is placed on top of the WD, and hydro turbines lead the water to the sea...

  16. Communicating Wave Energy: An Active Learning Experience for Students

    Science.gov (United States)

    Huynh, Trongnghia; Hou, Gene; Wang, Jin

    2016-01-01

    We have conducted an education project to communicate the wave energy concept to high school students. A virtual reality system that combines both hardware and software is developed in this project to simulate the buoy-wave interaction. This first-of-its-kind wave energy unit is portable and physics-based, allowing students to conduct a number of…

  17. The energy density of a Landau damped plasma wave

    NARCIS (Netherlands)

    Best, R. W. B.

    1999-01-01

    In this paper some theories about the energy of a Landau damped plasma wave are discussed and new initial conditions are proposed. Analysis of a wave packet, rather than an infinite wave, gives a clear picture of the energy transport from field to particles. Initial conditions are found which excite

  18. Modeling the Buoyancy System of a Wave Energy Power Plant

    DEFF Research Database (Denmark)

    Pedersen, Tom S.; Nielsen, Kirsten M.

    2009-01-01

    A nonlinear dynamic model of the buoyancy system in a wave energy power plant is presented. The plant ("Wave Dragon") is a floating device using the potential energy in overtopping waves to produce power. A water reservoir is placed on top of the WD, and hydro turbines lead the water to the sea...

  19. Operation and maintenance strategies for wave energy converters

    DEFF Research Database (Denmark)

    Ambühl, Simon; Marquis, Laurent; Kofoed, Jens Peter;

    2015-01-01

    Inspection and maintenance costs are a significant contributor to the cost of energy for wave energy converters. There are different operation and maintenance strategies for wave energy converters. Maintenance can be performed after failure (corrective) or before a breakdown (preventive) occurs...... and maintenance costs estimations for wave energy converter applications including real weather data and damage accumulation. Furthermore, uncertainties related with costs, structural damage accumulation, inspection accuracy and different maintenance strategies can be included. This article contains a case study...

  20. The radiation of surface wave energy: Implications for volcanic tremor

    Science.gov (United States)

    Haney, M. M.; Denolle, M.; Lyons, J. J.; Nakahara, H.

    2015-12-01

    The seismic energy radiated by active volcanism is one common measurement of eruption size. For example, the magnitudes of individual earthquakes in volcano-tectonic (VT) swarms can be summed and expressed in terms of cumulative magnitude, energy, or moment release. However, discrepancies exist in current practice when treating the radiated energy of volcano seismicity dominated by surface waves. This has implications for volcanic tremor, since eruption tremor typically originates at shallow depth and is made up of surface waves. In the absence of a method to compute surface wave energy, estimates of eruption energy partitioning between acoustic and seismic waves typically assume seismic energy is composed of body waves. Furthermore, without the proper treatment of surface wave energy, it is unclear how much volcanic tremor contributes to the overall seismic energy budget during volcanic unrest. To address this issue, we derive, from first principles, the expression of surface wave radiated energy. In contrast with body waves, the surface wave energy equation is naturally expressed in the frequency domain instead of the time domain. We validate our result by reproducing an analytical solution for the radiated power of a vertical force source acting on a free surface. We further show that the surface wave energy equation leads to an explicit relationship between energy and the imaginary part of the surface wave Green's tensor at the source location, a fundamental property recognized within the field of seismic interferometry. With the new surface wave energy equation, we make clear connections to reduced displacement and propose an improved formula for the calculation of surface wave reduced displacement involving integration over the frequency band of tremor. As an alternative to reduced displacement, we show that reduced particle velocity squared is also a valid physical measure of tremor size, one based on seismic energy rate instead of seismic moment rate. These

  1. CFD study of the overtopping discharge of the Wave Dragon wave energy converter

    DEFF Research Database (Denmark)

    Eskilsson, K.; Palm, J.; Kofoed, Jens Peter

    2015-01-01

    The Wave Dragon is a floating Wave Energy Converter (WEC) working by the overtopping principle. The overtopping discharge has been determined by model scale experiments in wave basins. In the present study we numerically simulate the overtopping behavior of the Wave Dragon device using a VOFbased...

  2. DISSIPATION OF WAVE ENERGY ON VERY MILD SLOPE

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper presents the analysis and calculation of wave attenuation when waves travel on sand bed, sand ripple bed and muddy bed, respectively. The study shows that (1) The dissipation of wave energy due to bottom percolation may be neglected on sand bed; (2) The wave attenuation due to the friction of sand ripples is one order higher than that of flat sand bed and (3) The energy loss of waves propagating on muddy bed is the largest. Then, the equivalent coefficients of friction are calculated in order to compare with the solution by the bottom-friction model. Wave attenuation are also computed by the Bingham-model and the principle of conservation of wave energy flux on very mild muddy slope. The results coincide well with the wave information from the Lianyungang Wave Observation Station. Theoretical prediction proves that the equivalent coefficients of friction strongly rely on water depth, which inerease with decreasing depth.

  3. Interferometric adaptive optics for high power laser pointing, wave-front control and phasing

    Energy Technology Data Exchange (ETDEWEB)

    Baker, K L; Stappaerts, E A; Homoelle, D C; Henesian, M A; Bliss, E S; Siders, C W; Barty, C J

    2009-01-21

    Implementing the capability to perform fast ignition experiments, as well as, radiography experiments on the National Ignition Facility (NIF) places stringent requirements on the control of each of the beam's pointing and overall wavefront quality. One quad of the NIF beams, 4 beam pairs, will be utilized for these experiments and hydrodynamic and particle-in-cell simulations indicate that for the fast ignition experiments, these beams will be required to deliver 50% (4.0 kJ) of their total energy (7.96 kJ) within a 40 {micro}m diameter spot at the end of a fast ignition cone target. This requirement implies a stringent pointing and overall phase conjugation error budget on the adaptive optics system used to correct these beam lines. The overall encircled energy requirement is more readily met by phasing of the beams in pairs but still requires high Strehl ratios, Sr, and rms tip/tilt errors of approximately one {micro}rad. To accomplish this task we have designed an interferometric adaptive optics system capable of beam pointing, high Strehl ratio and beam phasing with a single pixilated MEMS deformable mirror and interferometric wave-front sensor. We present the design of a testbed used to evaluate the performance of this wave-front sensor below along with simulations of its expected performance level.

  4. International Energy Agency Ocean Energy Systems Task 10 Wave Energy Converter Modeling Verification and Validation

    DEFF Research Database (Denmark)

    Wendt, Fabian F.; Yu, Yi-Hsiang; Nielsen, Kim

    2017-01-01

    This is the first joint reference paper for the Ocean Energy Systems (OES) Task 10 Wave Energy Converter modeling verification and validation group. The group is established under the OES Energy Technology Network program under the International Energy Agency. OES was founded in 2001 and Task 10 ...

  5. Wave propagation and energy dissipation in viscoelastic granular media

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In terms of viscoelasticity, the relevant theory of wave in granular media is analyzed in this paper.Under the conditions of slight deformation of granules, wave equation, complex number expressions of propagation vector and attenuation vector, attenuation coefficient expressions of longitudinal wave and transverse wave,etc, are analyzed and deduced. The expressions of attenuation coefficients of viscoelastic longitudinal wave and transverse wave show that the attenuation of wave is related to frequency. The higher the frequency is, the more the attenuation is, which is tested by the laboratory experiment. In addition, the energy dissipation is related to the higher frequency wave that is absorbed by granular media. The friction amongst granular media also increase the energy dissipation. During the flowing situation the expression of transmission factor of energy shows that the granular density difference is the key factor which leads to the attenuation of vibrating energy.This has been proved by the experiment results.

  6. Energy supply technologies. Hydro, ocean, wave and tidal

    Energy Technology Data Exchange (ETDEWEB)

    Fenhann, J.; Larsen, Hans [Risoe National Lab. - DTU (Denmark)

    2007-11-15

    stored wind energy, and could therefore form an interesting partnership with wind energy. Waves normally persist for six to eight hours after the wind drops, potentially allowing wave power to smooth out some of the variability inherent in wind power. Wave power could in the long term make an important contribution to the world's energy demand, if it can be developed to the point where it is technically and economically feasible. A potential 2,000 TWh/year, or 10 % of global electricity consumption, has been estimated, with predicted electricity costs of 0.08 Euro kWh. Denmark has been active in developing wave power technology such as Wave Dragon and Wave Star. These demonstration projects are excellent starting points for the further development of this promising technology. (BA)

  7. Experimental Study on the Langlee Wave Energy Converter

    DEFF Research Database (Denmark)

    Lavelle, John; Kofoed, Jens Peter

    This report concerns the experimental study of the 1:20 scale model of the Langlee Wave Energy Converter (WEC) carried out at Aalborg University’s wave basin during the summer of 2010.......This report concerns the experimental study of the 1:20 scale model of the Langlee Wave Energy Converter (WEC) carried out at Aalborg University’s wave basin during the summer of 2010....

  8. Energy dissipation through wind-generated breaking waves

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shuwen; CAO Ruixue; XIE Lingling

    2012-01-01

    Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attributed to wind-generated breaking waves,in terms of ratio of energy dissipation to energy input,windgenerated wave spectrum,and wave growth rate.Also advanced is a vertical distribution model of turbulent kinetic energy,based on an exponential distribution method.The result shows that energy dissipation rate depends heavily on wind speed and sea state.Our results agree well with predictions of previous works.

  9. Study of the potential of wave energy in Malaysia

    Science.gov (United States)

    Tan, Wan Ching; Chan, Keng Wai; Ooi, Heivin

    2017-07-01

    Renewable energy is generally defined as energy harnessed from resources which are naturally replenished. It is an alternative to the current conventional energy sources such as natural gas, oil and coal, which are nonrenewable. Besides being nonrenewable, the harnessing of these resources generally produce by-products which could be potentially harmful to the environment. On the contrary, the generation from renewable energy does not pose environmental degradation. Some examples of renewable energy sources are sunlight, wind, tides, waves and geothermal heat. Wave energy is considered as one of the most promising marine renewable resources and is becoming commercially viable quicker than other renewable technologies at an astonishing growth rate. This paper illustrates the working principle of wave energy converter (WEC) and the availability of wave energy in Malaysia oceans. A good understanding of the behaviour of ocean waves is important for designing an efficient WEC as the characteristics of the waves in shallow and deep water are different. Consequently, wave energy converters are categorized into three categories on shore, near shore and offshore. Therefore, the objectives of this study is ought to be carried out by focusing on the formation of waves and wave characteristics in shallow as well as in deep water. The potential sites for implementation of wave energy harvesting technology in Malaysia and the wave energy available in the respective area were analysed. The potential of wave energy in Malaysia were tabulated and presented with theoretical data. The interaction between motion of waves and heave buoys for optimum phase condition by using the mass and diameter as the variables were investigated.

  10. Causality and conjugate points in general plane waves

    Energy Technology Data Exchange (ETDEWEB)

    Flores, J L; Sanchez, M [Departamento de Geometria y Topologia, Facultad de Ciencias, Universidad de Granada, Avenida Fuentenueva s/n, 18071 Granada (Spain)

    2003-06-07

    Let M = M{sub 0} x R{sup 2} be a pp-wave-type spacetime endowed with the metric ({center_dot}, {center_dot}){sub z} = ({center_dot}, {center_dot}){sub x} + 2 du dv + H(x, u) du{sup 2}, where (M{sub 0}, ({center_dot}, {center_dot}){sub x}) is any Riemannian manifold and H(x, u) is an arbitrary function. We show that the behaviour of H(x, u) at spatial infinity determines the causality of M, say: (a) if -H(x, u) behaves subquadratically (i.e, essentially -H(x, u) {<=} R{sub 1}(u)|x|{sup 2-{epsilon}} for some {epsilon} > 0 and large distance |x| to a fixed point) and the spatial part (M{sub 0}, ({center_dot}, {center_dot}){sub x}) is complete, then the spacetime M is globally hyperbolic, (b) if -H(x, u) grows at most quadratically (i.e, -H(x, u) {<=} R{sub 1}(u)|x|{sup 2} for large |x|) then it is strongly causal and (c) M is always causal, but there are non-distinguishing examples (and thus, not strongly causal), even when -H(x, u) {<=} R{sub 1}(u)|x|{sup 2+{epsilon}}, for small {epsilon} > 0. Therefore, the classical model M{sub 0} = R{sup 2}, H(x, u) = {sigma}{sub i,j} h{sub ij}(u)x{sub i}x{sub j} {ne} 0), which is known to be strongly causal but not globally hyperbolic, lies in the critical quadratic situation with complete M{sub 0}. This must be taken into account for realistic applications. In fact, we argue that -H will be subquadratic (and the spacetime globally hyperbolic) if M is asymptotically flat. The relation of these results with the notion of astigmatic conjugacy and the existence of conjugate points is also discussed.

  11. Wave Energy Converter Annual Energy Production Uncertainty Using Simulations

    Directory of Open Access Journals (Sweden)

    Clayton E. Hiles

    2016-09-01

    Full Text Available Critical to evaluating the economic viability of a wave energy project is: (1 a robust estimate of the electricity production throughout the project lifetime and (2 an understanding of the uncertainty associated with said estimate. Standardization efforts have established mean annual energy production (MAEP as the metric for quantification of wave energy converter (WEC electricity production and the performance matrix approach as the appropriate method for calculation. General acceptance of a method for calculating the MAEP uncertainty has not yet been achieved. Several authors have proposed methods based on the standard engineering approach to error propagation, however, a lack of available WEC deployment data has restricted testing of these methods. In this work the magnitude and sensitivity of MAEP uncertainty is investigated. The analysis is driven by data from simulated deployments of 2 WECs of different operating principle at 4 different locations. A Monte Carlo simulation approach is proposed for calculating the variability of MAEP estimates and is used to explore the sensitivity of the calculation. The uncertainty of MAEP ranged from 2%–20% of the mean value. Of the contributing uncertainties studied, the variability in the wave climate was found responsible for most of the uncertainty in MAEP. Uncertainty in MAEP differs considerably between WEC types and between deployment locations and is sensitive to the length of the input data-sets. This implies that if a certain maximum level of uncertainty in MAEP is targeted, the minimum required lengths of the input data-sets will be different for every WEC-location combination.

  12. Wave energy devices with compressible volumes.

    Science.gov (United States)

    Kurniawan, Adi; Greaves, Deborah; Chaplin, John

    2014-12-08

    We present an analysis of wave energy devices with air-filled compressible submerged volumes, where variability of volume is achieved by means of a horizontal surface free to move up and down relative to the body. An analysis of bodies without power take-off (PTO) systems is first presented to demonstrate the positive effects a compressible volume could have on the body response. Subsequently, two compressible device variations are analysed. In the first variation, the compressible volume is connected to a fixed volume via an air turbine for PTO. In the second variation, a water column separates the compressible volume from another volume, which is fitted with an air turbine open to the atmosphere. Both floating and bottom-fixed, axisymmetric, configurations are considered, and linear analysis is employed throughout. Advantages and disadvantages of each device are examined in detail. Some configurations with displaced volumes less than 2000 m(3) and with constant turbine coefficients are shown to be capable of achieving 80% of the theoretical maximum absorbed power over a wave period range of about 4 s.

  13. Numerical modelling in wave energy conversion systems

    Energy Technology Data Exchange (ETDEWEB)

    El Marjani, A. [Labo. de Turbomachines, Ecole Mohammadia d' Ingenieurs (EMI), Universite Mohammed V Agdal, Av Ibn Sina, B.P. 765 Agdal, Rabat (Morocco); Castro Ruiz, F.; Rodriguez, M.A.; Parra Santos, M.T. [Depto. de Ingenieria Energetica y Fluidomecanica, Escuela Tecnica Superior de Ingenieros Industriales, Universidad de Valladolid, Paseo del Cauce s/n, E-47011 Valladolid (Spain)

    2008-08-15

    This paper deals with a numerical modelling devoted to predict the flow characteristics in the components of an oscillating water column (OWC) system used for the wave energy capture. In the present paper, the flow behaviour is modelled by using the FLUENT code. Two numerical flow models have been elaborated and tested independently in the geometries of an air chamber and a turbine, which is chosen of a radial impulse type. The flow is assumed to be three-dimensional (3D), viscous, turbulent and unsteady. The FLUENT code is used with a solver of the coupled conservation equations of mass, momentum and energy, with an implicit time scheme and with the adoption of the dynamic mesh and the sliding mesh techniques in areas of moving surfaces. Turbulence is modelled with the k-{epsilon} model. The obtained results indicate that the developed models are well suitable to analyse the air flows both in the air chamber and in the turbine. The performances associated with the energy transfer processes have been well predicted. For the turbine, the numerical results of pressure and torque were compared to the experimental ones. Good agreements between these results have been observed. (author)

  14. Experimental Study on the Langlee Wave Energy Converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter; Weisz, A.

    This report presents the results of an experimental study of the wave energy converting abilities of the Langlee wave energy converter (WEC). It focused mainly on evaluating the power generating capabilities of the device, including investigations of the following issues: Scaling ratiosPTO loadingWave...... height and wave period dependencyOblique incoming waves and directional spreading of waves (3D waves)Damping platesMooring forces and fixed structure setupPitch, surge and heave motion During the study the model supplied by the client (Langlee Wave Power AS) has been heavily instrumented - up to 23...... different instruments was deployed to measure and record data. Tests were performed at scales of 1:30 and 1:20 based on the realized reference wave states....

  15. Wave energy resource assessment based on satellite observations around Indonesia

    Science.gov (United States)

    Ribal, Agustinus; Zieger, Stefan

    2016-06-01

    A preliminary assessment of wave energy resource around Indonesian's ocean has been carried out by means of analyzing satellite observations. The wave energy flux or wave power can be approximated using parameterized sea states. Wave power scales with significant wave height, characteristic wave period and water depth. In this approach, the significant wave heights were obtained from ENVISAT (Environmental Satellite) data which have been calibrated. However, as the characteristic wave period is rarely specified and therefore must be estimated from other variables when information about the wave spectra is unknown. Here, the characteristic wave period was calculated with an empirical model that utilizes altimeter estimates of wave height and backscatter coefficient originally proposed. For the Indonesian region, wave power energy is calculated over two periods of one year each and was compared with the results from global hindcast carried out with a recent release of wave model WAVEWATCH III. We found that, the most promising wave power energy regions around the Indonesian archipelago are located in the south of Java island and the south west of Sumatera island. In these locations, about 20 - 30 kW/m (90th percentile: 30-50 kW/m, 99th percentile: 40-60 kW/m) wave power energy on average has been found around south of Java island during 2010. Similar results have been found during 2011 at the same locations. Some small areas which are located around north of Irian Jaya (West Papua) are also very promising and need further investigation to determine its capacity as a wave energy resource.

  16. Magnetoacoustic Waves in a Stratified Atmosphere with a Magnetic Null Point

    Science.gov (United States)

    Tarr, Lucas A.; Linton, Mark; Leake, James

    2017-03-01

    We perform nonlinear MHD simulations to study the propagation of magnetoacoustic waves from the photosphere to the low corona. We focus on a 2D system with a gravitationally stratified atmosphere and three photospheric concentrations of magnetic flux that produce a magnetic null point with a magnetic dome topology. We find that a single wavepacket introduced at the lower boundary splits into multiple secondary wavepackets. A portion of the packet refracts toward the null owing to the varying Alfvén speed. Waves incident on the equipartition contour surrounding the null, where the sound and Alfvén speeds coincide, partially transmit, reflect, and mode-convert between branches of the local dispersion relation. Approximately 15.5% of the wavepacket’s initial energy (E input) converges on the null, mostly as a fast magnetoacoustic wave. Conversion is very efficient: 70% of the energy incident on the null is converted to slow modes propagating away from the null, 7% leaves as a fast wave, and the remaining 23% (0.036E input) is locally dissipated. The acoustic energy leaving the null is strongly concentrated along field lines near each of the null’s four separatrices. The portion of the wavepacket that refracts toward the null, and the amount of current accumulation, depends on the vertical and horizontal wavenumbers and the centroid position of the wavepacket as it crosses the photosphere. Regions that refract toward or away from the null do not simply coincide with regions of open versus closed magnetic field or regions of particular field orientation. We also model wavepacket propagation using a WKB method and find that it agrees qualitatively, though not quantitatively, with the results of the numerical simulation.

  17. Energy budget of surface waves in the global ocean

    Institute of Scientific and Technical Information of China (English)

    TENG Yong; YANG Yongzeng; QIAO Fangli; LU Jing; YIN Xunqiang

    2009-01-01

    Mechanical energy input from atmosphere and losses from wave-breaking dissipation of sea surface waves are estimated by a direct scheme. This scheme is based on the integration in the wavenumber space of the wind input and breaking dissipation source functions of the MASNUM wave model.The global amount of wind energy input, averaged in 2005, is about 57 TW, and the wave-breaking dissipation summed in deep-water is about 33 TW, over a half of the wind energy input. The residual may be dissipated by beach processes. Global distributions of the energy input and breaking dissipation concentrate in the westerlies of the Southern Hemisphere.

  18. Stakeholder requirements for commercially successful wave energy converter farms

    Energy Technology Data Exchange (ETDEWEB)

    Babarit, Aurélien; Bull, Diana; Dykes, Katherine; Malins, Robert; Nielsen, Kim; Costello, Ronan; Roberts, Jesse; Bittencourt Ferreira, Claudio; Kennedy, Ben; Weber, Jochem

    2017-12-01

    In this study, systems engineering techniques are applied to wave energy to identify and specify stakeholders' requirements for a commercially successful wave energy farm. The focus is on the continental scale utility market. Lifecycle stages and stakeholders are identified. Stakeholders' needs across the whole lifecycle of the wave energy farm are analyzed. A list of 33 stakeholder requirements are identified and specified. This list of requirements should serve as components of a technology performance level metric that could be used by investors and funding agencies to make informed decisions when allocating resources. It is hoped that the technology performance level metric will accelerate wave energy conversion technology convergence.

  19. Wave energy resource assessment and review of the technologies

    Energy Technology Data Exchange (ETDEWEB)

    Wan Nik, W.B.: Sulaiman, O.O. [Maritime Technology Department, Universiti Malaysia Terengganu, 21030, Kuala Terengganu (Malaysia); Rosliza, R. [TATI University College, Teluk Kalong, 24000 Kemaman, Terengganu, (Malaysia); Prawoto, Y. [Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 UTM, Skudai, Johor (Malaysia); Muzathik, A.M. [Institute of Technology, University of Moratuwa (Sri Lanka)

    2011-07-01

    Increase in human population has increased the demand for more energy. Technical improvement in transport and electrical appliances gives a lot of facilities to our life nowadays. Still we need to generate or convert this energy. Energy generation based on conventional technologies is always accompanied by environmental pollution. It gives overheating and greenhouse effects that later result in biosphere degradation. Nowadays sea wave energy is being increasingly regarded in many countries as a major and promising resource. It is renewable and environmentally friendly. In this paper wave parameters related to wave energy is analyzed. Then the paper describes the development of many different types of wave-energy converters. Several topics are addressed; the characterization of the wave energy resource, range of devices and how such devices can be organized into classes.

  20. A Novel Complementary Method for the Point-Scan Nondestructive Tests Based on Lamb Waves

    Directory of Open Access Journals (Sweden)

    Rahim Gorgin

    2014-01-01

    Full Text Available This study presents a novel area-scan damage identification method based on Lamb waves which can be used as a complementary method for point-scan nondestructive techniques. The proposed technique is able to identify the most probable locations of damages prior to point-scan test which lead to decreasing the time and cost of inspection. The test-piece surface was partitioned with some smaller areas and the damage probability presence of each area was evaluated. A0 mode of Lamb wave was generated and collected using a mobile handmade transducer set at each area. Subsequently, a damage presence probability index (DPPI based on the energy of captured responses was defined for each area. The area with the highest DPPI value highlights the most probable locations of damages in test-piece. Point-scan nondestructive methods can then be used once these areas are found to identify the damage in detail. The approach was validated by predicting the most probable locations of representative damages including through-thickness hole and crack in aluminum plates. The obtained experimental results demonstrated the high potential of developed method in defining the most probable locations of damages in structures.

  1. Linear and nonlinear MHD mode coupling of the fast magnetoacoustic wave about a 3D magnetic null point

    Science.gov (United States)

    Thurgood, J. O.; McLaughlin, J. A.

    2012-09-01

    Context. Coronal magnetic null points have been implicated as possible locations for localised heating events in 2D models. We investigate this possibility about fully 3D null points. Aims: We investigate the nature of the fast magnetoacoustic wave about a fully 3D magnetic null point, with a specific interest in its propagation, and we look for evidence of MHD mode coupling and/or conversion to the Alfvén mode. Methods: A special fieldline and flux-based coordinate system was constructed to permit the introduction of a pure fast magnetoacoustic wave in the vicinity of proper and improper 3D null points. We considered the ideal, β = 0, MHD equations, which are solved using the LARE3D numerical code. The constituent modes of the resulting wave were isolated and identified using the special coordinate system. Numerical results were supported by analytical work derived from perturbation theory and a linear implementation of the WKB method. Results: An initially pure fast wave is found to be permanently decoupled from the Alfvén mode both linearly and nonlinearly for both proper and improper 3D null points. The pure fast mode also generates and sustains a nonlinear disturbance aligned along the equilibrium magnetic field. The resulting pure fast magnetoacoustic pulse has transient behaviour, which is found to be governed by the (equilibrium) Alfvén-speed profile, and a refraction effect focuses all the wave energy towards the null point. Conclusions: Thus, the main results from previous 2D work do indeed carry over to the fully 3D magnetic null points and so we conclude that 3D null points are locations for preferential heating in the corona by 3D fast magnetoacoustic waves.

  2. Coordinated Control of Wave Energy Converters Subject to Motion Constraints

    Directory of Open Access Journals (Sweden)

    Liguo Wang

    2016-06-01

    Full Text Available In this paper, a generic coordinated control method for wave energy converters is proposed, and the constraints on motion amplitudes and the hydrodynamic interaction between converters are considered. The objective of the control problem is to maximize the energy converted from ocean waves, and this is achieved by coordinating the power take-off (PTO damping of each wave energy converter in the frequency domain in each sea state. In a case study, a wave energy farm consisting of four converters based on the concept developed by Uppsala University is studied. In the solution, motion constraints, including constraints on the amplitudes of displacement and velocity, are included. Twelve months of sea states, based on measured wave data at the Lysekil test site on the Swedish west coast, are used in the simulation to evaluate the performance of the wave energy farm using the new method. Results from the new coordinated control method and traditional control method are compared, indicating that the coordinated control of wave energy converters is an effective way to improve the energy production of wave energy farm in harmonic waves.

  3. Climate change impact on wave energy in the Persian Gulf

    Science.gov (United States)

    Kamranzad, Bahareh; Etemad-Shahidi, Amir; Chegini, Vahid; Yeganeh-Bakhtiary, Abbas

    2015-06-01

    Excessive usage of fossil fuels and high emission of greenhouse gases have increased the earth's temperature, and consequently have changed the patterns of natural phenomena such as wind speed, wave height, etc. Renewable energy resources are ideal alternatives to reduce the negative effects of increasing greenhouse gases emission and climate change. However, these energy sources are also sensitive to changing climate. In this study, the effect of climate change on wave energy in the Persian Gulf is investigated. For this purpose, future wind data obtained from CGCM3.1 model were downscaled using a hybrid approach and modification factors were computed based on local wind data (ECMWF) and applied to control and future CGCM3.1 wind data. Downscaled wind data was used to generate the wave characteristics in the future based on A2, B1, and A1B scenarios, while ECMWF wind field was used to generate the wave characteristics in the control period. The results of these two 30-yearly wave modelings using SWAN model showed that the average wave power changes slightly in the future. Assessment of wave power spatial distribution showed that the reduction of the average wave power is more in the middle parts of the Persian Gulf. Investigation of wave power distribution in two coastal stations (Boushehr and Assalouyeh ports) indicated that the annual wave energy will decrease in both stations while the wave power distribution for different intervals of significant wave height and peak period will also change in Assalouyeh according to all scenarios.

  4. Nonlinear dynamics of wave packets in PT-symmetric optical lattices near the phase transition point

    CERN Document Server

    Nixon, Sean; Yang, Jianke

    2012-01-01

    Nonlinear dynamics of wave packets in PT-symmetric optical lattices near the phase-transition point are analytically studied. A nonlinear Klein-Gordon equation is derived for the envelope of these wave packets. A variety of novel phenomena known to exist in this envelope equation are shown to also exist in the full equation including wave blowup, periodic bound states and solitary wave solutions.

  5. Scattered surface wave energy in the seismic coda

    Science.gov (United States)

    Zeng, Y.

    2006-01-01

    One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda. Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves. When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later arrival times for deeper events.

  6. Fermi energy-dependence of electromagnetic wave absorption in graphene

    Science.gov (United States)

    Shoufie Ukhtary, M.; Hasdeo, Eddwi H.; Nugraha, Ahmad R. T.; Saito, Riichiro

    2015-05-01

    Undoped graphene is known to absorb 2.3% of visible light at a normal angle of incidence. In this paper, we theoretically demonstrate that the absorption of 10-100 GHz of an electromagnetic wave can be tuned from nearly 0 to 100% by varying the Fermi energy of graphene when the angle of incidence of the electromagnetic wave is kept within total internal reflection geometry. We calculate the absorption probability of the electromagnetic wave as a function of the Fermi energy of graphene and the angle of incidence of the wave. These results open up possibilities for the development of simple electromagnetic wave-switching devices operated by gate voltage.

  7. Deployment Effects of Marine Renewable Energy Technologies: Wave Energy Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Mirko Previsic

    2010-06-17

    Given proper care in siting, design, deployment, operation and maintenance, wave energy conversion could become one of the more environmentally benign sources of electricity generation. In order to accelerate the adoption of these emerging hydrokinetic and marine energy technologies, navigational and environmental concerns must be identified and addressed. All developing hydrokinetic projects involve a wide variety of stakeholders. One of the key issues that site developers face as they engage with this range of stakeholders is that, due to a lack of technical certainty, many of the possible conflicts (e.g., shipping and fishing) and environmental issues are not well-understood,. In September 2008, re vision consulting, LLC was selected by the Department of Energy (DoE) to apply a scenario-based assessment to the emerging hydrokinetic technology sector in order to evaluate the potential impact of these technologies on the marine environment and navigation constraints. The project’s scope of work includes the establishment of baseline scenarios for wave and tidal power conversion at potential future deployment sites. The scenarios capture variations in technical approaches and deployment scales to properly identify and characterize environmental effects and navigational effects. The goal of the project is to provide all stakeholders with an improved understanding of the potential range of technical attributes and potential effects of these emerging technologies and focus all stakeholders on the critical issues that need to be addressed. By identifying and addressing navigational and environmental concerns in the early stages of the industry’s development, serious mistakes that could potentially derail industry-wide development can be avoided. This groundwork will also help in streamlining siting and associated permitting processes, which are considered key hurdles for the industry’s development in the U.S. today. Re vision is coordinating its efforts with two

  8. Wave energy budget analysis in the Earth's radiation belts uncovers a missing energy.

    Science.gov (United States)

    Artemyev, A V; Agapitov, O V; Mourenas, D; Krasnoselskikh, V V; Mozer, F S

    2015-05-15

    Whistler-mode emissions are important electromagnetic waves pervasive in the Earth's magnetosphere, where they continuously remove or energize electrons trapped by the geomagnetic field, controlling radiation hazards to satellites and astronauts and the upper-atmosphere ionization or chemical composition. Here, we report an analysis of 10-year Cluster data, statistically evaluating the full wave energy budget in the Earth's magnetosphere, revealing that a significant fraction of the energy corresponds to hitherto generally neglected very oblique waves. Such waves, with 10 times smaller magnetic power than parallel waves, typically have similar total energy. Moreover, they carry up to 80% of the wave energy involved in wave-particle resonant interactions. It implies that electron heating and precipitation into the atmosphere may have been significantly under/over-valued in past studies considering only conventional quasi-parallel waves. Very oblique waves may turn out to be a crucial agent of energy redistribution in the Earth's radiation belts, controlled by solar activity.

  9. 3D Alfvén wave behaviour about proper and improper magnetic null points

    Science.gov (United States)

    Thurgood, J. O.; McLaughlin, J. A.

    2013-10-01

    Context. Magnetohydrodynamic (MHD) waves and magnetic null points are both prevalent in many astrophysical plasmas, including the solar atmosphere. Interaction between waves and null points has been implicated as a possible mechanism for localised heating events. Aims: Here we investigate the transient behaviour of the Alfvén wave about fully 3D proper and improper magnetic null points. Methods: We introduce an Alfvén wave into the vicinity of both proper and improper null points by numerically solving the ideal, β = 0 MHD equations using the LARE3D code. A magnetic fieldline and flux-based coordinate system permits the isolation of resulting wave modes and the analysis of their interaction. Results: We find that the Alfvén wave propagates throughout the region and accumulates near the fan-plane, causing current build up. For different values of null point eccentricity, the qualitative behaviour changes only by the imposition of anisotropic pulse dilation, owing to the differing rates at which fieldlines diverge from the spine. For all eccentricities, we find that the fast and Alfvén waves are linearly decoupled. During the driving phase, an independently propagating fast wave is nonlinearly generated owing to the ponderomotive force. Subsequently, no further excitation of fast waves occurs. Conclusions: We find that the key aspects of the theory of Alfvén waves about 2D null points extends intuitively to the fully 3D case; i.e. the wave propagates along fieldlines and thus accumulates at predictable parts of the topology. We also highlight that unlike in the 2D case, in 3D Alfvén-wave pulses are always toroidal, and thus any aspects of 2D Alfvén-wave-null models that are pulse-geometry specific must be reconsidered in 3D.

  10. Experimental Modelling of the Overtopping Flow on the Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Kofoed, Jens Peter

    The Wave Dragon is a floating slack-moored Wave Energy Converter (WEC) of the overtopping type. Oncoming waves are focused by two wing reflectors towards the ramp of the device, surge-up and overtop into a reservoir placed at a higher level than the surface of the sea. The energy production takes...... place as the water is led back to the sea through a set of low-head hydro-turbines. After many years of development, Wave Dragon (WD) is now facing the phase of pre-commercial demonstration. In this phase it is very important to be able to use the available data to predict the performances of the device...... at different scales and locations. A flexible and comprehensive modelling tool is therefore highly required. Wave Dragon produces power through different steps of energy conversion: 1. Primary energy conversion: overtopping – The energy content of the wave (partly in the kinetic and partly in the potential...

  11. Experimental investigation of rubble mound breakwaters for wave energy conversion

    DEFF Research Database (Denmark)

    Luppa, C.; Contestabile, P.; Cavallaro, L.

    2015-01-01

    The paper describes recent laboratory investigation on the breakwater integrated device named “OBREC” (Overtopping BReakwater for Energy Conversion). This technology recently appeared on the wave energy converter scene as an executive outcome of improving composite seawalls by including overtopping...... type wave energy converters [1]. Two complementary experimental campaigns were carried out, in 2012 and in 2014. Several geometries and wave conditions were examined. Preliminary comparison of hydraulic behaviour has been summarized, focusing on reflection analysis and overtopping flow rate......-by-wave measurement of couples of hydraulic head-flow rate acting on a virtual turbine inlet. Finally, the influence of draft length on overtopping discharge has been identified....

  12. q-Deformed Boson Oscillators and Zero Point Energy

    OpenAIRE

    Swamy, P. Narayana

    1999-01-01

    Just as for the ordinary quantum harmonic oscillators, we expect the zero-point energy to play a crucial role in the correct high temperature behavior. We accordingly reformulate the theory of the statistical distribution function for the q-deformed boson oscillators and develop an approximate theory incorporating the zero-point energy. We are then able to demonstrate that for small deformations, the theory reproduces the correct limits both for very high temperatures and for very low tempera...

  13. Minimising the lifetime carbon and energy intensities of the Oyster wave energy converter

    OpenAIRE

    Steynor, Jeffrey Robert

    2014-01-01

    Converting energy from ocean waves is an exciting concept aimed at reducing our dependency on fossil fuels. Ocean energy devices must convert the large forces and relatively small movements from ocean waves into electrical power with a minimum carbon and energy intensity in order to be economically viable. The research herein focuses on the Oyster, a flap-type pitching wave energy converter developed by Aquamarine Power. A device that has the minimal carbon or energy intensi...

  14. Toward Best Practices for Public Acceptability in Wave Energy

    DEFF Research Database (Denmark)

    Stefanovichu, M. A.; Chozas, Julia Fernandez

    2010-01-01

    At this initial stage of development, opinion toward wave energy is mainly positive. Interviews with developers, presentations about wave energy at local community meetings, and the literature show that there are four main types of issues developers need to address when discussing their projects ...

  15. Innovative rubble mound breakwaters for overtopping wave energy conversion

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Contestabile, Pasquale; Nørgaard, Jørgen Quvang Harck

    2014-01-01

    This paper intends contributing to the development of an economically and environmentally sustainable coastal infrastructure, which combines rubble mound breakwaters with Wave Energy Converters (WEC). The energy is produced by collecting wave overtopping in a front reservoir, which is returned to...

  16. An Appraisal of the DEXA Wave Energy Converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter

    This report has been requested by VækstFonden and aims at giving an overview of the experimental tests and a general appraisal of the DEXA wave energy converter (WEC). The reported results and findings were obtained during previously performed experimental tests by the Wave Energy Research Group...

  17. Toward Best Practices for Public Acceptability in Wave Energy

    DEFF Research Database (Denmark)

    Stefanovichu, M. A.; Chozas, Julia Fernandez

    2010-01-01

    At this initial stage of development, opinion toward wave energy is mainly positive. Interviews with developers, presentations about wave energy at local community meetings, and the literature show that there are four main types of issues developers need to address when discussing their projects ...

  18. Maximum power point tracking for optimizing energy harvesting process

    Science.gov (United States)

    Akbari, S.; Thang, P. C.; Veselov, D. S.

    2016-10-01

    There has been a growing interest in using energy harvesting techniques for powering wireless sensor networks. The reason for utilizing this technology can be explained by the sensors limited amount of operation time which results from the finite capacity of batteries and the need for having a stable power supply in some applications. Energy can be harvested from the sun, wind, vibration, heat, etc. It is reasonable to develop multisource energy harvesting platforms for increasing the amount of harvesting energy and to mitigate the issue concerning the intermittent nature of ambient sources. In the context of solar energy harvesting, it is possible to develop algorithms for finding the optimal operation point of solar panels at which maximum power is generated. These algorithms are known as maximum power point tracking techniques. In this article, we review the concept of maximum power point tracking and provide an overview of the research conducted in this area for wireless sensor networks applications.

  19. Wave Energy Dissipation of Waves Breaking on a Reef with a Steep Front Slope

    DEFF Research Database (Denmark)

    Jensen, M.S.; Burcharth, Hans F.; Brorsen, Michael

    2005-01-01

    The Transformation of waves propagating over a steep bottom slope is of great importance regarding the coastal processes in the near-shore area.This study will contribute with tools to predict the dissipated wave energy for irregular waves passing a steep submerged slope. An extensive number...... of test with regular and irregular waves breaking over a steep bottom slope have been performed in the Hydraulics & Coastal Engineering Laboratory, Aalborg University. Based on these experimental data formulae have been developed capable of predicting he transmitted wave energy over steep slopes....

  20. 3 Years Experience with Energy Production on the Nissum Bredning Wave Dragon Prototype

    DEFF Research Database (Denmark)

    Frigaard, Peter; Tedd, James; Kofoed, Jens Peter

    2006-01-01

    Wave Dragon is a floating wave energy converter working by extracting energy principally by means of overtopping of waves into a reservoir. A 1:4.5 scale prototype has been sea tested for 20 months. This paper presents results from testing, experiences gained and developments made during...... this extended period. The prototype is highly instrumented. The overtopping characteristic and the power produced are presented here. This has enabled comparison between the prototype and earlier results from both laboratory model and computer simulation. This gives the optimal operating point and the expected...

  1. Experimental study of ultrasonic beam sectors for energy conversion into Lamb waves and Rayleigh waves.

    Science.gov (United States)

    Declercq, Nico Felicien

    2014-02-01

    When a bounded beam is incident on an immersed plate Lamb waves or Rayleigh waves can be generated. Because the amplitude of a bounded beam is not constant along its wave front, a specific beam profile is formed that influences the local efficiency of energy conversion of incident sound into Lamb waves or Rayleigh waves. Understanding this phenomenon is important for ultrasonic immersion experiments of objects because the quality of such experiments highly depends on the amount of energy transmitted into the object. This paper shows by means of experiments based on monochromatic Schlieren photography that the area within the bounded beam responsible for Lamb wave generation differs from that responsible for Rayleigh wave generation. Furthermore it provides experimental verification of an earlier numerical study concerning Rayleigh wave generation.

  2. Influence of Wave State Uncertainties on Probabilistic Reliability Assessments of Wave Energy Devices

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kofoed, Jens Peter; Sørensen, John Dalsgaard

    2013-01-01

    Probabilistic reliability assessments of wave energy devices (WEDs) need to consider, among others, uncertainties related to the wave states, which are often defined by the significant wave height HS and the peak period TP or the mean crossing wave period TZ or the energy period Te. Based...... on the JONSWAP spectrum and white noise filtering, wave elevation time series are generated and uncertainties related to the wave states are estimated. In this paper, uncertainties regarding the time series length used to characterize a certain wave state, uncertainties related to the JONSWAP spectrum parameters...... and the influence on wave state discretization in a scatter diagram are assessed. The estimated uncertainties are then implemented in two generic structural reliability assessments with focus on fatigue and extreme failure modes. The resulting reliability indices are compared with related industries like offshore...

  3. Wave Energy Dissipation by Permeable and Impermeable Submerged Breakwaters

    Directory of Open Access Journals (Sweden)

    Yonguk Ryu

    2016-01-01

    Full Text Available The purpose of this study was to investigate the effect of the porosity of a submerged breakwater on wave fields, including snapshots of the wave, velocity profiles of the water over the structure, and the kinetic energy of the wave. Two-dimensional experiments were conducted for submerged trapezoidal breakwaters with impermeable and permeable layers in a two-dimensional wave tank. The flow fields obtained by the particle image velocimetry (PIV technique are presented to understand the flow characteristics due to the waves’ interactions with the submerged impermeable and permeable breakwaters, and these characteristics showed that the vertical velocity dominant flow occurred under the crest of the wave. In addition, the kinetic energies were compared for different porosities and wave conditions. The comparisons of the wave flow fields and kinetic energy distributions showed that the different pattern of the dissipated kinetic energy was dependent on the porosity. The dissipation of kinetic energy also was observed to increase as the wave period increased. The comparisons indicated that greater amounts of energy were dissipated for longer wave periods.

  4. Survivability mode and extreme loads on the mooring lines of the Wave Dragon Wave Energy Converter

    Energy Technology Data Exchange (ETDEWEB)

    Parmeggiani, S.; Kofoed, J.P.

    2010-11-15

    This report is a product of the cooperation agreement between Wave Dragon and Aalborg University regarding phase 2 of the development of the Wave Dragon Wave Energy Converter. The research is carried out by testing the 1:51.8 scale model of the Wave Dragon, aiming at the assessment of the survivability of the device in extreme waves and evaluation of the design loads for the mooring component. The outcome of the research will be used as input for future research work aimed at the design of the mooring system and the certification of the structural design for the full scale Wave Dragon demonstrator. (Author)

  5. Quenched Point-to-Point Free Energy for Random Walks in Random Potentials

    CERN Document Server

    Rassoul-Agha, Firas

    2012-01-01

    We consider a random walk in a random potential on a square lattice of arbitrary dimension. The potential is a function of an ergodic environment and some steps of the walk. The potential can be unbounded, but it is subject to a moment assumption whose strictness is tied to the mixing of the environment, the best case being the i.i.d. environment. We prove that the infinite volume quenched point-to-point free energy exists and has a variational formula in terms of an entropy. We establish regularity properties of the point-to-point free energy, as a function of the potential and as a function on the convex hull of the admissible steps of the walk, and link it to the infinite volume free energy and quenched large deviations of the endpoint of the walk. One corollary is a quenched large deviation principle for random walk in an ergodic random environment, with a continuous rate function.

  6. Reliability-Based Structural Optimization of Wave Energy Converters

    Directory of Open Access Journals (Sweden)

    Simon Ambühl

    2014-12-01

    Full Text Available More and more wave energy converter (WEC concepts are reaching prototypelevel. Once the prototype level is reached, the next step in order to further decrease thelevelized cost of energy (LCOE is optimizing the overall system with a focus on structuraland maintenance (inspection costs, as well as on the harvested power from the waves.The target of a fully-developed WEC technology is not maximizing its power output,but minimizing the resulting LCOE. This paper presents a methodology to optimize thestructural design of WECs based on a reliability-based optimization problem and the intentto maximize the investor’s benefits by maximizing the difference between income (e.g., fromselling electricity and the expected expenses (e.g., structural building costs or failure costs.Furthermore, different development levels, like prototype or commercial devices, may havedifferent main objectives and will be located at different locations, as well as receive varioussubsidies. These points should be accounted for when performing structural optimizationsof WECs. An illustrative example on the gravity-based foundation of the Wavestar deviceis performed showing how structural design can be optimized taking target reliability levelsand different structural failure modes due to extreme loads into account.

  7. Energy Relations for Plane Waves Reflected from Moving Media

    DEFF Research Database (Denmark)

    Daly, P.; Gruenberg, Harry

    1967-01-01

    When a plane wave is obliquely incident from vacuum on a semi-infinite moving medium, the energy flow carried by the incident wave, is in general, not carried away by the reflected and transmitted waves. This is only the case when the medium velocity is parallel to its vacuum interface. Otherwise...... there is a net inflow or outflow of electromagnetic energy, which can be accounted for by the change of stored energy in the system, and the work done by the mechanical forces acting on the medium. A detailed energy balance is drawn up for two different media moving normal to their vacuum interfaces: (a...

  8. Enhancing Wave Energy Competitiveness through Co-Located Wind and Wave Energy Farms. A Review on the Shadow Effect

    Directory of Open Access Journals (Sweden)

    Sharay Astariz

    2015-07-01

    Full Text Available Wave energy is one of the most promising alternatives to fossil fuels due to the enormous available resource; however, its development may be slowed as it is often regarded as uneconomical. The largest cost reductions are expected to be obtained through economies of scale and technological progress. In this sense, the incorporation of wave energy systems into offshore wind energy farms is an opportunity to foster the development of wave energy. The synergies between both renewables can be realised through these co-located energy farms and, thus, some challenges of offshore wind energy can be met. Among them, this paper focuses on the longer non-operational periods of offshore wind turbines—relative to their onshore counterparts—typically caused by delays in maintenance due to the harsh marine conditions. Co-located wave energy converters would act as a barrier extracting energy from the waves and resulting in a shielding effect over the wind farm. On this basis, the aim of this paper is to analyse wave energy economics in a holistic way, as well as the synergies between wave and offshore wind energy, focusing on the shadow effect and the associated increase in the accessibility to the wind turbines.

  9. Electricity from wave and tide an introduction to marine energy

    CERN Document Server

    Lynn, Paul A

    2014-01-01

    This is a concise yet technically authoritative overview of modern marine energy devices with the goal of sustainable electricity generation. With 165 full-colour illustrations and photographs of devices at an advanced stage, the book provides inspiring case studies of today's most promising marine energy devices and developments, including full-scale grid-connected prototypes tested in sea conditions. It also covers the European Marine Energy Centre (EMEC) in Orkney, Scotland, where many of the devices are assessed. Topics discussed: global resources - drawing energy from the World's waves and tides history of wave and tidal stream systems theoretical background to modern developments conversion of marine energy into grid electricity modern wave energy converters and tidal stream energy converters. This book is aimed at a wide readership including professionals, policy makers and employees in the energy sector needing an introduction to marine energy. Its descriptive style and technical level will also appea...

  10. Propagation of gravitational waves in an expanding background in the presence of a point mass

    CERN Document Server

    Antoniou, I; Perivolaropoulos, L

    2016-01-01

    We solve the Laplace equation $\\Box h_{ij}=0$ describing the propagation of gravitational waves in an expanding background metric with a power law scale factor in the presence of a point mass in the weak field approximation (Newtonian McVittie background). We use boundary conditions at large distances from the mass corresponding to a plane gravitational wave in an expanding background. We compare the solution with the corresponding solution in the absence of the point mass and show that the point mass increases the amplitude of the wave and also decreases its frequency (as observed by an observer at infinity) in accordance with gravitational time delay.

  11. Do laser interferometers absorb energy from gravitational waves ?

    CERN Document Server

    Ma, Yiqiu; Zhao, Chunnong; Kells, William

    2014-01-01

    In this paper we discuss the energy interaction between gravitational waves and laser interferom- eter gravitational wave detectors. We show that the widely held view that the laser interferometer gravitational wave detector absorbs no energy from gravitational waves is only valid under the approximation of a frequency-independent optomechanical coupling strength and a pump laser without detuning with respect to the resonance of the interferometer. For a strongly detuned interferometer, the optical-damping dynamics dissipates gravitational wave energy through the interaction between the test masses and the optical ?eld. For a non-detuned interferometer, the frequency-dependence of the optomechanical coupling strength causes a tiny energy dissipation, which is proved to be equivalent to the Doppler friction raised by Braginsky et.al.

  12. Integration of Wave Energy Converters into Coastal Protection Schemes

    DEFF Research Database (Denmark)

    Zanuttigh, B.; Martinelli, L.; Castagnetti, M.

    2010-01-01

    The purpose of this paper is to examine the feasibility of using wave energy converters for coastal protection through laboratory tests. The paper considers the case of a near-shore floating device of the Wave Activated Body type, named DEXA. The influence of the device length and of the wave...... parameters on device efficiency and on inshore wave transmission are investigated. A preliminary design procedure to optimise both device efficiency and wave transmission is proposed by means of an hypothetical application to the Adriatic coast. The effects induced by the device on coastal morphology...

  13. Wave Loadings Acting on an Innovative Breakwater for Energy Production

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Ciardulli, F.; Buccino, M.

    2011-01-01

    The paper reports on 2D small scale experiments conducted to investigate wave loadings acting on a pilot project of device for the conversion of wave energy into electricity. The conversion concept is based on the overtopping principle and the structure is worldwide known with the acronym SSG....... The hydraulic model tests have been carried out at the LInC laboratory of the University of Naples Federico II using random waves. Results indicate wave overtopping is able to cause a sudden inversion of vertical force under wave crest, so that it is alternatively upward and downward directed over a short time...

  14. Structural Modeling and Analysis of a Wave Energy Converter

    DEFF Research Database (Denmark)

    Zurkinden, Andrew Stephen; Lambertsen, Søren Heide; Damkilde, Lars

    2012-01-01

    A fatigue analysis is being carried out for a wave energy converter subjected to ocean wave loads. The device is a bottom fixed structure, located in a shallow water environment. Interest is focused on the local stress response of a structural detail and a subsequent calculation of its fatigue life...... by using the rainflow counting approach. The wave energy converter is characterized by its ability to enter in a storm protection mode which - whenever extreme conditions occur - will drastically reduce the exposure to wave loads. The predicted fatigue life is calculated for two different control cases...

  15. Coincidences between gravitational wave interferometers and high energy neutrino telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Pradier, Thierry [Institut Pluridisciplinaire Hubert Curien (IPHC/DRS), University Louis-Pasteur, Strasbourg (France)], E-mail: pradier@in2p3.fr

    2009-04-11

    Sources of gravitational waves (GW) and emitters of high energy neutrinos (HE {nu}) both involve compact objects and matter moving at relativistic speeds. GW emission requires a departure from spherical symmetry, which is the case if clumps of matter are accreted around black holes or neutron stars, and ejected in relativistic jets, where neutrinos are believed to be produced. Both messengers interact weakly with the surrounding matter, hence point directly to the heart of the engines that power these emissions. Coincidences between GW interferometers (e.g. VIRGO) and HE {nu} telescopes (e.g. ANTARES) would then give a unique insight on the physics of the most powerful objects in the Universe. The possibility, observability and detectability for such GW/HE {nu} coincidences are analysed.

  16. High-frequency waves in the corona due to null points

    Science.gov (United States)

    Santamaria, I. C.; Khomenko, E.; Collados, M.; de Vicente, A.

    2017-06-01

    This work aims to understand the behavior of non-linear waves in the vicinity of a coronal null point. In previous works we have shown that high-frequency waves are generated in such a magnetic configuration. This paper studies those waves in detail in order to provide a plausible explanation of their generation. We demonstrate that slow magneto-acoustic shock waves generated in the chromosphere propagate through the null point and produce a train of secondary shocks that escape along the field lines. A particular combination of the shock wave speeds generates waves at a frequency of 80 mHz. We speculate that this frequency may be sensitive to the atmospheric parameters in the corona and therefore can be used to probe the structure of this solar layer. Movies attached to Figs 2 and 4 are available at http://www.aanda.org

  17. Innovative wave energy device applied to coastal observatory systems

    Science.gov (United States)

    Marcelli, Marco; Bonamano, Simone; Piermattei, Viviana; Scanu, Sergio; Paladini de Mendoza, Francesco; Martellucci, Riccardo; Maximo, Peviani

    2017-04-01

    Marine environment is one of the most promising sources of renewable energy, whose exploitation could have an effect on several application fields. This work presents the design of an innovative device based on the Oscillating Water Column (OWC), that allows to convert wave energy into electricity, suitable for the typical Mediterranean wave climate. The flexibility of the device permits its installation either in deep or shallow waters, with reduced costs of deployment, maintenance and connection to the grid. Furthermore, the replicability of the design allows the device to be installed in array of several number of similar units. The technical concept is to convey the sea water within a vertical pipe, in which the water movements activate a rotor connected to a generator that transforms the energy of the water motion into electricity. The hydrodynamic design of the pipe is built to minimize the losses due to friction and turbulence and to exploit the maximum possible energy from wave motion. The wave energy is directly absorbed by the rotational movement of the turbine blades located in the water itself allowing a further reduction of the energy losses associated with the transformation of the linear water motion into electrical generation in the air phase (typical configuration of the OWC devices). In this work the device components are described considering two possible configurations that use a Wells turbine or a Bulb type turbine. The system can be realized at a low cost, because of the modularity of the device project, which allows large freedom of sizes and placements, being able to be installed both individually and in arrays. The modularity, associated with the fact that the main elements of the system are available on the market, makes the device particularly attractive from the economic point of view. Finally, it is realized with a high constructive flexibility: the proposed system can be transported floating and moored to existing coastal structures or

  18. Wave Energy Resource along the Coast of Santa Catarina (Brazil

    Directory of Open Access Journals (Sweden)

    Pasquale Contestabile

    2015-12-01

    Full Text Available Brazil has one of the largest electricity markets in South America, which needs to add 6000 MW of capacity every year in order to satisfy growing the demand from an increasing and more prosperous population. Apart from biomass, no other renewable energy sources, besides hydroelectricity, play a relevant role in the energy mix. The potential for wind and wave energy is very large. Brazil's Santa Catarina state government is starting a clean energy program in the state, which is expected to bring more than 1 GW of capacity. Assessment of wave energy resources is needed along the coastline. This work studied the potential wave energy along the north-central coasts of Santa Catarina, in Southern Brazil, by analysis of the hindcast data from the European Centre for Medium-Range Weather Forecasts (ECMWF. The annual offshore wave power was found to be equal to 15.25 kW/m, the bulk of which is provided by southeastern waves. The nearshore energetic patterns were studied by means of a numerical coastal propagation model (Mike21 SW. The mean wave power of 20 m isobaths is 11.43 kW/m. Supplementary considerations are drawn on realistic perspectives for wave energy converters installations.

  19. Response and energy dissipation of rock under stochastic stress waves

    Institute of Scientific and Technical Information of China (English)

    DENG Jian; BIAN Li

    2007-01-01

    The response and energy dissipation of rock under stochastic stress waves were analyzed based on dynamic fracture criterion of brittle materials integrating with Fourier transform methods of spectral analysis When the stochastic stress waves transnut through rocks,the frequency and energy ratio of harmonic components were calculated by analytical and discrete analysis methods.The stress waves in shale, malmstone and liparite were taken as examples to illustrate the proposed analysis methods.The results show the harder the rock, the less absorption of energy,the more the useless elastic waves transmitting through rock, and the narrower the cutoff frequency to fracture rock.When the whole stress energy doubles either by doubling the duration time or byincreasing the amplitude of stress wave, ratio of the energy of elastic waves transmitting through rock to me whole stress energy (i.e.energy dissipation ratio)is decreased to 10%-15%. When doubling the duration time.the cutoff frequency to fracture rock remains constant.However, with the increase of the amplitude of stress wave. the cutoff frequency increases accordingly.

  20. Low-energy point source searches with IceCube

    Directory of Open Access Journals (Sweden)

    Euler Sebastian

    2016-01-01

    Full Text Available Due to the overwhelming background of atmospheric muons, the traditional IceCube point source search in the Southern Hemisphere is mainly sensitive to neutrinos with energies above 100TeV. A new approach focuses on events starting inside the instrumented volume. By utilizing different veto techniques we are able to significantly reduce the energy threshold and can now for the first time explore the entire Southern Hemisphere at neutrino energies as low as 100GeV. We present the results of two analyses targeting slightly different energy ranges. Both use one year of data taken with the completed IceCube detector in 2011/12.

  1. Spatial localization of nonlinear waves spreading in materials in the presence of dislocations and point defects

    Science.gov (United States)

    Erofeev, V. I.; Leontieva, A. V.; Malkhanov, A. O.

    2017-06-01

    Within the framework of self consistent dynamic problems, the impact of dislocations and point defects on the spatial localization of nonlinear acoustic waves propagating in materials has been studied.

  2. Nonlinear Alfv\\'en wave dynamics at a 2D magnetic null point: ponderomotive force

    CERN Document Server

    Thurgood, J O

    2013-01-01

    Context : In the linear, {\\beta}=0 MHD regime, the transient properties of MHD waves in the vicinity of 2D null points are well known. The waves are decoupled and accumulate at predictable parts of the magnetic topology: fast waves accumulate at the null point; whereas Alfv\\'en waves cannot cross the separatricies. However, in nonlinear MHD mode conversion can occur at regions of inhomogeneous Alfv\\'en speed, suggesting that the decoupled nature of waves may not extend to the nonlinear regime. Aims: We investigate the behaviour of low-amplitude Alfv\\'en waves about a 2D magnetic null point in nonlinear, {\\beta}= 0 MHD. Methods: We numerically simulate the introduction of low-amplitude Alfv\\'en waves into the vicinity of a magnetic null point using the nonlinear LARE2D code. Results: Unlike in the linear regime, we find that the Alfv\\'en wave sustains cospatial daughter disturbances, manifest in the transverse and longitudinal fluid velocity, owing to the action of nonlinear magnetic pressure gradients (viz. t...

  3. Energy dissipation in magnetic null points at kinetic scales

    CERN Document Server

    Olshevsky, Vyacheslav; Eriksson, Elin; Markidis, Stefano; Lapenta, Giovanni

    2015-01-01

    We use kinetic particle-in-cell and magnetohydrodynamic simulations supported by an observational dataset to investigate magnetic reconnection in clusters of null points in space plasma. The magnetic configuration under investigation is driven by fast adiabatic flux rope compression that dissipates almost half of the initial magnetic field energy. In this phase powerful currents are excited producing secondary instabilities, and the system is brought into a state of `intermittent turbulence' within a few ion gyro-periods. Reconnection events are distributed all over the simulation domain and energy dissipation is rather volume-filling. Numerous spiral null points interconnected via their spines form null lines embedded into magnetic flux ropes; null point pairs demonstrate the signatures of torsional spine reconnection. However, energy dissipation mainly happens in the shear layers formed by adjacent flux ropes with oppositely directed currents. In these regions radial null pairs are spontaneously emerging an...

  4. 3D Alfven wave behaviour around proper and improper magnetic null points

    CERN Document Server

    Thurgood, J O

    2013-01-01

    Context: MHD waves and magnetic null points are both prevalent in many astrophysical plasmas, including the solar atmosphere. Interaction between waves and null points has been implicated as a possible mechanism for localised heating events. Aims: Here we investigate the transient behaviour of the Alfven wave about fully 3D proper and improper 3D magnetic null points. Previously, the behaviour of fast magnetoacoustic waves at null points in 3D, cold MHD was considered by Thurgood & McLaughlin (Astronomy & Astrophysics, 2012, 545, A9). Methods: We introduce an Alfven wave into the vicinity of both proper and improper null points by numerically solving the ideal, $\\beta=0$ MHD equations using the LARE3D code. A magnetic fieldline and flux-based coordinate system permits the isolation of resulting wave-modes and the analysis of their interaction. Results: We find that the Alfven wave propagates throughout the region and accumulates near the fan-plane, causing current build up. For different values of nul...

  5. On the wave energy potential of Western Black Sea shelf

    CERN Document Server

    Galabov, Vasko

    2013-01-01

    In the present study we evaluate the approaches to estimate the wave energy potential of the western Black Sea shelf with numerical models. For the purpose of our evaluation and due to the lack of long time series of measurements in the selected area of the Black Sea, we compare the modeled mean wave power flux output from the SWAN wave model with the only available long term measurements from the buoy of Gelendzhik for the period 1997-2003 (with gaps). The forcing meteorological data for the numerical wave models for the selected years is extracted from the ERA Interim reanalysis of ECMWF (European Centre for Medium range Forecasts). For the year 2003 we also compare the estimated wave power with the modeled by SWAN, using ALADIN regional atmospheric model winds. We try to identify the shortcomings and limitations of the numerical modeling approach to the evaluation of the wave energy potential in Black Sea.

  6. Fast Modeling of Large Wave Energy Farms Using Interaction Distance Cut-Off

    Directory of Open Access Journals (Sweden)

    Malin Göteman

    2015-12-01

    Full Text Available In many wave energy concepts, power output in the MW range requires the simultaneous operation of many wave energy converters. In particular, this is true for small point-absorbers, where a wave energy farm may contain several hundred devices. The total performance of the farm is affected by the hydrodynamic interactions between the individual devices, and reliable tools that can model full farms are needed to study power output and find optimal design parameters. This paper presents a novel method to model the hydrodynamic interactions and power output of very large wave energy farms. The method is based on analytical multiple scattering theory and uses time series of irregular wave amplitudes to compute the instantaneous power of each device. An interaction distance cut-off is introduced to improve the computational cost with acceptable accuracy. As an application of the method, wave energy farms with over 100 devices are studied in the MW range using one month of wave data measured at an off-shore site.

  7. Understanding zero-point energy in the context of classical electromagnetism

    Science.gov (United States)

    Boyer, Timothy H.

    2016-09-01

    Today’s textbooks of electromagnetism give the particular solution to Maxwell’s equations involving the integral over the charge and current sources at retarded times. However, the texts fail to emphasise that the choice of the incoming-wave boundary conditions corresponding to solutions of the homogeneous Maxwell equations must be made based upon experiment. Here we discuss the role of these incoming-wave boundary conditions for an experimenter with a hypothetical charged harmonic oscillator as his equipment. We describe the observations of the experimenter when located near a radio station or immersed in thermal radiation at temperature T. The classical physicists at the end of the 19th century chose the incoming-wave boundary conditions for the homogeneous Maxwell equations based upon the experimental observations of Lummer and Pringsheim which measured only the thermal radiation which exceeded the random radiation surrounding their measuring equipment; the physicists concluded that they could take the homogeneous solutions to vanish at zero temperature. Today at the beginning of the 21st century, classical physicists must choose the incoming-wave boundary conditions for the homogeneous Maxell equations to correspond to the full radiation spectrum revealed by the recent Casimir force measurements which detect all the radiation surrounding conducting parallel plates, including the radiation absorbed and emitted by the plates themselves. The random classical radiation spectrum revealed by the Casimir force measurements includes electromagnetic zero-point radiation, which is missing from the spectrum measured by Lummer and Pringsheim, and which cannot be eliminated by going to zero temperature. This zero-point radiation will lead to zero-point energy for all systems which have electromagnetic interactions. Thus the choice of the incoming-wave boundary conditions on the homogeneous Maxwell equations is intimately related to the ideas of zero-point energy and non

  8. Modelling of the Overtopping Flow on the Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Pecher, Arthur; Kofoed, Jens Peter

    2010-01-01

    The Wave Dragon is a floating slack-moored Wave Energy Converter of the overtopping type, which is facing now the last phase of development before the commercial exploitation: the deployment of a full-scale demonstrator. In this phase a modelling tool allowing for accurate predictions of the perf......The Wave Dragon is a floating slack-moored Wave Energy Converter of the overtopping type, which is facing now the last phase of development before the commercial exploitation: the deployment of a full-scale demonstrator. In this phase a modelling tool allowing for accurate predictions...

  9. Life cycle assessment of the wave energy converter: Wave Dragon

    DEFF Research Database (Denmark)

    Hans Chr., Sørensen; Stefan, Naef; Stefan, Anderberg

    Any power production technology should be able to demonstrate that it's able to comply with current and future environmental regulation and that it demonstrates a considerable surplus in the energy balance being a part of the entire power system. This means that the energy used throughout all...... the lifecycle stages; from provision of materials over manufacturing of components and assembly, to deployment and use and eventually the disposal stage, is considerably less than the energy produced by the devise during its use/production stage....

  10. A TAILORED FINITE POINT METHOD FOR THE HELMHOLTZ EQUATION WITH HIGH WAVE NUMBERS IN HETEROGENEOUS MEDIUM

    Institute of Scientific and Technical Information of China (English)

    Houde Han; Zhongyi Huang

    2008-01-01

    In this paper, we propose a tailored-finite-point method for the numerical simulation of the Helmholtz equation with high wave numbers in heterogeneous medium. Our finite point method has been tailored to some particular properties of the problem, which allows us to obtain approximate solutions with the same behaviors as that of the exact solution very naturally. Especially, when the coefficients are piecewise constant, we can get the exact solution with only one point in each subdomain. Our finite-point method has uniformly convergent rate with respect to wave number k in L2-norm.

  11. Sampling saddle points on a free energy surface.

    Science.gov (United States)

    Samanta, Amit; Chen, Ming; Yu, Tang-Qing; Tuckerman, Mark; E, Weinan

    2014-04-28

    Many problems in biology, chemistry, and materials science require knowledge of saddle points on free energy surfaces. These saddle points act as transition states and are the bottlenecks for transitions of the system between different metastable states. For simple systems in which the free energy depends on a few variables, the free energy surface can be precomputed, and saddle points can then be found using existing techniques. For complex systems, where the free energy depends on many degrees of freedom, this is not feasible. In this paper, we develop an algorithm for finding the saddle points on a high-dimensional free energy surface "on-the-fly" without requiring a priori knowledge the free energy function itself. This is done by using the general strategy of the heterogeneous multi-scale method by applying a macro-scale solver, here the gentlest ascent dynamics algorithm, with the needed force and Hessian values computed on-the-fly using a micro-scale model such as molecular dynamics. The algorithm is capable of dealing with problems involving many coarse-grained variables. The utility of the algorithm is illustrated by studying the saddle points associated with (a) the isomerization transition of the alanine dipeptide using two coarse-grained variables, specifically the Ramachandran dihedral angles, and (b) the beta-hairpin structure of the alanine decamer using 20 coarse-grained variables, specifically the full set of Ramachandran angle pairs associated with each residue. For the alanine decamer, we obtain a detailed network showing the connectivity of the minima obtained and the saddle-point structures that connect them, which provides a way to visualize the gross features of the high-dimensional surface.

  12. Search for the QCD critical point at SPS energies

    CERN Document Server

    Anticic, T; Barna, D; Bartke, J; Betev, L; Bialkowska, H; Blume, C; Boimska, B; Botje, M; Bracinik, J; Buncic, P; Cerny, V; Christakoglou, P; Chung, P; Chvala, O; Cramer, J G; Csato, P; Dinkelaker, P; Eckardt, V; Fodor, Z; Foka, P; Friese, V; Gal, J; Gazdzicki, M; Genchev, V; Gladysz, E; Grebieszkow, K; Hegyi, S; Hohne, C; Kadija, K; Karev, A; Kikola, D; Kolesnikov, V I; Kornas, E; Korus, R; Kowalski, M; Kreps, M; Laszlo, A; Lacey, R; van Leeuwen, M; Levai, P; Litov, L; Lungwitz, B; Makariev, M; Malakhov, A I; Mateev, M; Melkumov, G L; Mischke, A; Mitrovski, M; Mrowczynski, St; Nicolic, V; Palla, G; Panagiotou, A D; Petridis, A; Peryt, W; Pikna, M; Pluta, J; Prindle, D; Puhlhofer, F; Renfordt, R; Roland, C; Roland, G; Rybczynski, M; Rybicki, A; Sandoval, A; Schmitz, N; Schuster, T; Seyboth, P; Sikler, F; Sitar, B; Skrzypczak, E; Slodkowski, M; Stefanek, G; Stock, R; Strabel, C; Strobele, H; Susa, T; Szentpetery, I; Sziklai, J; Szuba, M; Szymanski, P; Trubnikov, V; Utvic, M; Varga, D; Vassiliou, M; Veres, G I; Vesztergombi, G; Vranic, D; Wlodarczyk, Z; Wojtaszek-Szwarc, A; Yoo, I K; Abgrall, N; Aduszkiewicz, A; Andrieu, B; Anticic, T; Antoniou, N; Argyriades, J; Asryan, A G; Baatar, B; Blondel, A; Blumer, J; Boldizsar, L; Bravar, A; Brzychczyk, J; Bubak, A; Bunyatov, S A; Choi, K.-U; Christakoglou, P; Chung, P; Cleymans, J; Derkach, D A; Diakonos, F; Dominik, W; Dumarchez, J; Engel, R; Ereditato, A; Feofilov, G A; Fodor, Z; Ferrero, A; Gazdzicki, M; Golubeva, M; Grebieszkow, K; Grzeszczuk, A; Guber, F; Hasegawa, T; Haungs, A; Igolkin, S; Ivanov, A S; Ivashkin, A; Kadija, K; Katrynska, N; Kielczewska, D; Kikola, D; Kisiel, J; Kobayashi, T; Kolesnikov, V I; Kolev, D; Kolevatov, R S; Kondratiev, V P; Kowalski, S; Kurepin, A; Lacey, R; Laszlo, A; Lyubushkin, V V; Majka, Z; Malakhov, A I; Marchionni, A; Marcinek, A; Maris, I; Matveev, V; Melkumov, G L; Meregaglia, A; Messina, M; Mijakowski, P; Mitrovski, M; Montaruli, T; Mrowczynski, St; Murphy, S; Nakadaira, T; Naumenko, P A; Nikolic, V; Nishikawa, K; Palczewski, T; Palla, G; Panagiotou, A D; Peryt, W; Planeta, R; Pluta, J; Popov, B A; Posiadala, M; Przewlocki, P; Rauch, W; Ravonel, M; Renfordt, R; Rohrich, D; Rondio, E; Rossi, B; Roth, M; Rubbia, A; Rybczynski, M; Sadovsky, A; Sakashita, K; Schuster, T; Sekiguchi, T; Seyboth, P; Shibata, M; Sissakian, A N; Skrzypczak, E; Slodkowski, M; Sorin, A S; Staszel, P; Stefanek, G; Stepaniak, J; Strabel, C; Stroebele, H; Susa, T; Szentpetery, I; Szuba, M; Tada, M; Taranenko, A; Tsenov, R; Ulrich, R; Unger, M; Vassiliou, M; Vechernin, V V; Vesztergombi, G; Wlodarczyk, Z; Wojtaszek-Szwarc, A; Zipper, W

    2009-01-01

    Lattice QCD calculations locate the QCD critical point at energies accessible at the CERN Super Proton Synchrotron (SPS). We present average transverse momentum and multiplicity fluctuations, as well as baryon and anti-baryon transverse mass spectra which are expected to be sensitive to effects of the critical point. The future CP search strategy of the NA61/SHINE experiment at the SPS is also discussed.

  13. pp-wave matrix models from point-like gravitons

    Energy Technology Data Exchange (ETDEWEB)

    Lozano, Y. [Departamento de Fisica, Universidad de Oviedo, Av. Calvo Sotelo 18, 33007 Oviedo (Spain); Rodriguez-Gomez, D. [Department of Physics, Princeton University, Princeton, NJ 08540 (United States)

    2007-05-15

    The BFSS Matrix model can be regarded as a theory of coincident M-theory gravitons. In this spirit, we summarize how using the action for coincident gravitons proposed in hep-th/0207199 it is possible to go beyond the linear order approximation of Kabat and Taylor, and to provide a satisfactory microscopical description of giant gravitons in AdS{sub m} x S{sup n} backgrounds. We then show that in the M-theory maximally supersymmetric pp-wave background, the action for coincident gravitons, besides reproducing the BMN Matrix model, predicts a new quadrupolar coupling to the M-theory 6-form potential, which supports the so far elusive fuzzy 5-sphere giant graviton solution. Finally, we discuss similar Matrix models that can be derived in Type II string theories using dualities. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  14. Pp-wave Matrix Models from Point-like Gravitons

    CERN Document Server

    Lozano, Y; Lozano, Yolanda; Rodriguez-Gomez, Diego

    2007-01-01

    The BFSS Matrix model can be regarded as a theory of coincident M-theory gravitons. In this spirit, we summarize how using the action for coincident gravitons proposed in hep-th/0207199 it is possible to go beyond the linear order approximation of Kabat and Taylor, and to provide a satisfactory microscopical description of giant gravitons in $AdS_m\\times S^n$ backgrounds. We then show that in the M-theory maximally supersymmetric pp-wave background, the action for coincident gravitons, besides reproducing the BMN Matrix model, predicts a new quadrupolar coupling to the M-theory 6-form potential, which supports the so far elusive fuzzy 5-sphere giant graviton solution. Finally, we discuss similar Matrix models that can be derived in Type II string theories using dualities.

  15. Wave energy power take off system control and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Zhoul, Z.; Holland, P.M.; Igic, P. [Swansea Univ., Swansea, Wales (United Kingdom). School of Engineering; Knapp, W. [Technische Univ. Muenchen, Munich (Germany); MacEnri, J. [ESB International, Dublin (Ireland); Srensen, H.Ch.; Friis-Madsen, E. [Wave Dragon APS and LTD, Copenhagen (Denmark)

    2008-07-01

    The generation of electric power from wave energy using an offshore wave energy take-off system has received global interest. Several different wave energy take off techniques have been suggested. Among these, the Wave Dragon is one of the most efficient wave energy conversion systems. This paper presented a wave energy power take off system control and simulation scheme. The characteristics of low pressure hydro turbine were described. A variable speed control scheme using IGBT alternating current/direct current converter for low-head hydro-turbine was described in order to achieve maximum efficiency. The electrical system configuration, operation and grid connection issues were presented. Last, in order to investigate the long electro-mechanical process, a simulation model was developed for simulating the generator-turbine starting-stop process. The simulated parameters included the effects of the water head on the torque, speed and output power. Simulation results were presented and discussed. It was concluded that the proposed model is suitable for investigating the overall performance of a wave energy power take off system. 12 refs., 14 figs.

  16. Quantifying the Benefits of Combining Offshore Wind and Wave Energy

    Science.gov (United States)

    Stoutenburg, E.; Jacobson, M. Z.

    2009-12-01

    For many locations the offshore wind resource and the wave energy resource are collocated, which suggests a natural synergy if both technologies are combined into one offshore marine renewable energy plant. Initial meteorological assessments of the western coast of the United States suggest only a weak correlation in power levels of wind and wave energy at any given hour associated with the large ocean basin wave dynamics and storm systems of the North Pacific. This finding indicates that combining the two power sources could reduce the variability in electric power output from a combined wind and wave offshore plant. A combined plant is modeled with offshore wind turbines and Pelamis wave energy converters with wind and wave data from meteorological buoys operated by the US National Buoy Data Center off the coast of California, Oregon, and Washington. This study will present results of quantifying the benefits of combining wind and wave energy for the electrical power system to facilitate increased renewable energy penetration to support reductions in greenhouse gas emissions, and air and water pollution associated with conventional fossil fuel power plants.

  17. Spectacular X-ray Jet Points Toward Cosmic Energy Booster

    Science.gov (United States)

    2000-06-01

    NASA's Chandra X-ray Observatory has revealed a spectacular luminous spike of X rays that emanates from the vicinity of a giant black hole in the center of the radio galaxy Pictor A. The spike, or jet, is due to a beam of particles that streaks across hundreds of thousands of light years of intergalactic space toward a brilliant X-ray hot spot that marks its end point. Pictor A Image Press Image and Caption The hot spot is at least 800 thousand light years (8 times the diameter of our Milky Way galaxy) away from where the jet originates. It is thought to represent the advancing head of the jet, which brightens conspicuously where it plows into the tenuous gas of intergalactic space. The jet, powered by the giant black hole, originates from a region of space no bigger than the solar system. "Both the brightness and the spectrum of the X rays are very different from what theory predicts," Professor Andrew Wilson reported today at the 196th national meeting of the American Astronomical Society in Rochester, New York. Wilson, of the University of Maryland, College Park, along with Dr. Patrick Shopbell and Dr. Andrew Young, also of the University of Maryland, are submitting an article on this research to the Astrophysical Journal. "The Chandra observations are telling us that something out there is producing many more high-energy particles than we expected," said Wilson. One possible explanation for the X rays is that shock waves along the side and head of the X-ray jet are accelerating electrons and possibly protons to speeds close to that of light. In the process the electrons are boosted to energies as high as 100 million times their own rest mass energy. These electrons lose their energy rapidly as they produce X rays, so this could be the first direct evidence of this process so far outside a galaxy. The hot spot has been seen with optical and radio telescopes. Radio telescopes have also observed a faint jet. Jets are thought to be produced by the extreme

  18. What can wave energy learn from offshore oil and gas?

    Science.gov (United States)

    Jefferys, E R

    2012-01-28

    This title may appear rather presumptuous in the light of the progress made by the leading wave energy devices. However, there may still be some useful lessons to be learnt from current 'offshore' practice, and there are certainly some awful warnings from the past. Wave energy devices and the marine structures used in oil and gas exploration as well as production share a common environment and both are subject to wave, wind and current loads, which may be evaluated with well-validated, albeit imperfect, tools. Both types of structure can be designed, analysed and fabricated using similar tools and technologies. They fulfil very different missions and are subject to different economic and performance requirements; hence 'offshore' design tools must be used appropriately in wave energy project and system design, and 'offshore' cost data should be adapted for 'wave' applications. This article reviews the similarities and differences between the fields and highlights the differing economic environments; offshore structures are typically a small to moderate component of field development cost, while wave power devices will dominate overall system cost. The typical 'offshore' design process is summarized and issues such as reliability-based design and design of not normally manned structures are addressed. Lessons learned from poor design in the past are discussed to highlight areas where care is needed, and wave energy-specific design areas are reviewed. Opportunities for innovation and optimization in wave energy project and device design are discussed; wave energy projects must ultimately compete on a level playing field with other routes to low CO₂ energy and/or energy efficiency. This article is a personal viewpoint and not an expression of a ConocoPhillips position.

  19. Interaction of two walkers: wave-mediated energy and force.

    Science.gov (United States)

    Borghesi, Christian; Moukhtar, Julien; Labousse, Matthieu; Eddi, Antonin; Fort, Emmanuel; Couder, Yves

    2014-12-01

    A bouncing droplet, self-propelled by its interaction with the waves it generates, forms a classical wave-particle association called a "walker." Previous works have demonstrated that the dynamics of a single walker is driven by its global surface wave field that retains information on its past trajectory. Here we investigate the energy stored in this wave field for two coupled walkers and how it conveys an interaction between them. For this purpose, we characterize experimentally the "promenade modes" where two walkers are bound and propagate together. Their possible binding distances take discrete values, and the velocity of the pair depends on their mutual binding. The mean parallel motion can be either rectilinear or oscillating. The experimental results are recovered analytically with a simple theoretical framework. A relation between the kinetic energy of the droplets and the total energy of the standing waves is established.

  20. Variations of wave energy power in shoaling zone of Benin coastal zone

    Directory of Open Access Journals (Sweden)

    Mathias A. Houekpoheha

    2015-02-01

    Full Text Available Today, we observe at the population level, that the improvement in comfort is accompanied by an increase in the electrical energy required. The predicted exhaustion of fossil energy resources maintains some speculation. Their unequal geographical distribution justifies the energy dependence of Benin overlooked from outside. So it is urgent to explore the various sources of renewable energy available to Benin. In this work, using measurements made ​​by the Millennium Challenge Account (MCA-Benin as part of the extension of the port of Cotonou, with Boussinesq equations (Peregrine and Stokes waves dispersion relation, we characterized the variations of various swell parameters (height, wavelength, velocities in the shoaling zone on the study site and proceeded to estimate variations in wave energy power from deep waters to the bathymetric breaking point. Finally, the zone with high energy power (where the conversion of this energy into electrical energy would be profitable of these waves is highlighted on the site, the local water depth at the point of breaking waves is evaluated and results obtained allowed to justify the very energetic character take by these swells on this coast when they are close to the beach.

  1. Identifying nonlinear wave interactions in plasmas using two-point measurements a case study of Short Large Amplitude Magnetic Structures (SLAMS)

    CERN Document Server

    Dudok de Wit, T; Dunlop, M; Luehr, H

    1999-01-01

    A framework is described for estimating Linear growth rates and spectral energy transfers in turbulent wave-fields using two-point measurements. This approach, which is based on Volterra series, is applied to dual satellite data gathered in the vicinity of the Earth's bow shock, where Short Large Amplitude Magnetic Structures (SLAMS) supposedly play a leading role. The analysis attests the dynamic evolution of the SLAMS and reveals an energy cascade toward high-frequency waves.

  2. Observations of nearshore infragravity wave dynamics under high energy swell and wind-wave conditions

    Science.gov (United States)

    Inch, Kris; Davidson, Mark; Masselink, Gerd; Russell, Paul

    2017-04-01

    Infragravity waves (0.005-0.04 Hz) can dominate the water motion close to shore on low sloping beaches and play a significant role in beach and dune erosion. A new field data set of water surface elevation at 15 cross-shore locations on a dissipative, fetch-unlimited beach is analysed to investigate the forcing and surf zone behaviour of infragravity waves during a wide range of offshore wave conditions (Ho=0.38-3.88 m; Tp=6-20 s). Infragravity waves approach the shore as bound waves lagging slightly ( 4 s) behind the short wave (0.04-0.33 Hz) envelope and are released in the surf zone as free waves. Infragravity wave heights of up to 1 m are measured close to shore and are best predicted using an offshore forcing parameter that represents the short wave energy flux (Ho2 Tp). Considerable infragravity dissipation is observed in the surf zone and dissipation increases with offshore wave energy. Dissipation is highly frequency-dependant and a frequency-domain Complex Empirical Orthogonal Function analysis reveals (quasi-)standing waves at frequencies <0.017 Hz, but an increasingly progressive wave pattern at higher frequencies with reflection coefficients <0.1, indicative of more than 90% dissipation. Much of the observed dissipation occurs very close to shore and the dependence of the reflection coefficient on a normalised bed slope parameter implies that energy at high infragravity frequencies is dissipated by wave breaking, since these frequencies fit into a mild sloping regime. This is supported by the results of bispectral analysis which show predominantly infragravity-infragravity interactions in shallow water and the development of infragravity harmonics indicative of steepening and eventual breaking of the infragravity waves.

  3. Wave Protection Effect of Periodic Row of Bottom-Hinged Flap-Type Wave Energy Converters

    Institute of Scientific and Technical Information of China (English)

    王冬姣; 邱守强; 叶家玮; 梁富琳

    2016-01-01

    A flap-type wave energy converter(WEC) is combined with a nearshore breakwater to expand the ap-plication of WECs both economically and environmentally. Based on the linear potential theory, an eigenfunction expansion solution is developed for a periodic row of bottom-hinged flap-type WECs exposed to normal waves. Additionally, the viscous effect is considered using the ship rolling solution method with a viscous damping term included in the equation of motion, and the viscous damping expression is also described. The proposed solution is verified by comparison with published literatures. The results including the wave energy conversion efficiency, the reflected and transmitted proportion of the incident wave energy are presented for a range of wave periods and geometric ratios. It is demonstrated that better wave protection effects can be attained with smaller gaps between the WECs, where the transmitted proportion of the incident wave energy is lower. An optimal geometric ratio thus exists for a given wave power absorption and a specific wave period.

  4. Simplified Design Procedures for Moorings of Wave-Energy Converters

    DEFF Research Database (Denmark)

    Bergdahl, Lars; Kofoed, Jens Peter

    The goal of the report is that the reader shall be able to self-dependently make a first, preliminary analysis of wave-induced horizontal loads, motions and mooring forces for a moored floating wave energy device. Necessary prerequisites to attain that goal are the understanding of the physical...

  5. Experimental Study of the WEPTOS Wave Energy Converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter; Marchalot, Tanguy

    This report presents the results of an experimental study on the power conversion capabilities and structural loads of the WEPTOS wave energy converter. The investigation focuses mainly at identifying the performance of the WEPTOS prototype in a wide range of production wave states and at the moo...

  6. Anomalous waves in gas-liquid mixtures near gas critical point in Gardner equation approximation

    Science.gov (United States)

    Gasenko, V. G.

    2016-10-01

    The waves in a bubbled incompressible liquid with Van der Waals gas in a bubbles being near critical points is considered in a frame of Gardner equation. It is shown that both coefficients on quadratic and cubic nonlinear terms in Gardner equation change the sign near gas critical point and it results the anomalous waves: negative and limited solitons, kinks, antikinks and breathers. The dynamics and interactions of these waves was studied numerically by high accuracy Fourier methods with periodically boundary conditions. In particular it is revealed that limited solitons always arise from initial distribution with a few identical soliton's pair and stand stable in their form after numerous interactions.

  7. Specification of Instrumentation of Multi MW Wave Dragon Offshore Wave Energy Converter

    DEFF Research Database (Denmark)

    Gilling, Lasse; Kofoed, Jens Peter

    Wave Dragon is a wave energy converter of the overtopping type and is described e.g. in Tedd et. al. (2006). The device has been thoroughly tested on a 1:51.8 scale model in wave laboratories and a 1:4.5 scale model deployed in Nissum Bredning, a large inland waterway in Denmark. Based on the exp......Wave Dragon is a wave energy converter of the overtopping type and is described e.g. in Tedd et. al. (2006). The device has been thoroughly tested on a 1:51.8 scale model in wave laboratories and a 1:4.5 scale model deployed in Nissum Bredning, a large inland waterway in Denmark. Based...

  8. Concept Study of Foundation Systems for Wave Energy Converters

    DEFF Research Database (Denmark)

    Molina, Salvador Devant; Vaitkunaite, Evelina; Ibsen, Lars Bo

    Analysis of possible foundation solution for Wave Energy Converters (WEC) is presented by investigating and optimizing novel foundation systems recently developed for offshore wind turbines. Gravity based, pile and bucket foundations are innovative foundation systems that are analyzed. Concept...

  9. Model Predictive Control of Buoy Type Wave Energy Converter

    DEFF Research Database (Denmark)

    Soltani, Mohsen N.; Sichani, Mahdi T.; Mirzaei, Mahmood

    2014-01-01

    The paper introduces the Wavestar wave energy converter and presents the implementation of model predictive controller that maximizes the power generation. The ocean wave power is extracted using a hydraulic electric generator which is connected to an oscillating buoy. The power generator...... is an additive device attached to the buoy which may include damping, stiffness or similar terms hence will affect the dynamic motion of the buoy. Therefore such a device can be seen as a closed-loop controller. The objective of the wave energy converter is to harvest as much energy from sea as possible....... This approach is then taken into account and an MPC controller is designed for a model wave energy converter and implemented on a numerical example. Further, the power outtake of this controller is compared to the optimal controller as an indicator of the performance of the designed controller....

  10. Global infinite energy solutions for the cubic wave equation

    OpenAIRE

    Burq, N.; L. Thomann; Tzvetkov, N.

    2012-01-01

    International audience; We prove the existence of infinite energy global solutions of the cubic wave equation in dimension greater than 3. The data is a typical element on the support of suitable probability measures.

  11. Optimising Reactive Control in non-ideal Efficiency Wave Energy Converters

    DEFF Research Database (Denmark)

    Strager, Thomas; Lopez, Pablo Fernandez; Giorgio, Giuseppe

    2014-01-01

    When analytically optimising the control strategy in wave energy converters which use a point absorber, the efficiency aspect is generally neglected. The results presented in this paper provide an analytical expression for the mean harvested electrical power in non-ideal efficiency situations...

  12. On Mooring Solutions for Large Wave Energy Converters

    DEFF Research Database (Denmark)

    Thomsen, Jonas Bjerg; Kofoed, Jens Peter; Ferri, Francesco

    2017-01-01

    The present paper describes the work carried out in the project ’Mooring Solutions for Large Wave Energy Converters’, which is a Danish research project carried out in a period of three years from September 2014, with the aim of reducing cost of the moorings for four wave energy converters......-model based optimization process with the aim of optimizing the mooring layout for each WEC according to cost of the systems....

  13. Extreme Loads on the Mooring Lines and Survivability Mode for the Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Kofoed, Jens Peter; Friis-Madsen, E.

    2011-01-01

    One of the main challenges Wave Energy Converters have to face on the road towards commercialization is to ensure survivability in extreme condition at a reasonable capital costs. For a floating device like the Wave Dragon, a reliable mooring system is essential. The control strategy of the Wave...... by approximately 20-30% by lowering the crest level and balancing the device to lean a little towards the front....

  14. Reprint of : Dynamics of a quantum wave emitted by a decaying and evanescent point source

    Science.gov (United States)

    Delgado, F.; Muga, J. G.

    2016-08-01

    We put forward a model that describes a decaying and evanescent point source of non-interacting quantum waves in 1D. This point-source assumption allows for a simple description that captures the essential aspects of the dynamics of a wave traveling through a classically forbidden region without the need to specify the details of the inner region. The dynamics of the resulting wave is examined and several characteristic times are identified. One of them generalizes the tunneling time-scale introduced by Büttiker and Landauer and it characterizes the arrival of the maximum of the wave function. Diffraction in time and deviations from exponential decay are also studied. Here we show that there exists an optimal injection frequency and detection point for the observation of these two quantum phenomena.

  15. ENERGY DISSIPATION IN MAGNETIC NULL POINTS AT KINETIC SCALES

    Energy Technology Data Exchange (ETDEWEB)

    Olshevsky, Vyacheslav; Lapenta, Giovanni [Centre for Mathematical Plasma Astrophysics (CmPA), KU Leuven (Belgium); Divin, Andrey [Department of Physics, St. Petersburg State University (Russian Federation); Eriksson, Elin [Swedish Institute of Space Physics, Uppsala Division, Uppsala (Sweden); Markidis, Stefano, E-mail: sya@mao.kiev.ua [High Performance Computing and Visualization (HPCViz), KTH Royal Institute of Technology, Stockholm (Sweden)

    2015-07-10

    We use kinetic particle-in-cell and MHD simulations supported by an observational data set to investigate magnetic reconnection in clusters of null points in space plasma. The magnetic configuration under investigation is driven by fast adiabatic flux rope compression that dissipates almost half of the initial magnetic field energy. In this phase powerful currents are excited producing secondary instabilities, and the system is brought into a state of “intermittent turbulence” within a few ion gyro-periods. Reconnection events are distributed all over the simulation domain and energy dissipation is rather volume-filling. Numerous spiral null points interconnected via their spines form null lines embedded into magnetic flux ropes; null point pairs demonstrate the signatures of torsional spine reconnection. However, energy dissipation mainly happens in the shear layers formed by adjacent flux ropes with oppositely directed currents. In these regions radial null pairs are spontaneously emerging and vanishing, associated with electron streams and small-scale current sheets. The number of spiral nulls in the simulation outweighs the number of radial nulls by a factor of 5–10, in accordance with Cluster observations in the Earth's magnetosheath. Twisted magnetic fields with embedded spiral null points might indicate the regions of major energy dissipation for future space missions such as the Magnetospheric Multiscale Mission.

  16. Energy Dissipation in Magnetic Null Points at Kinetic Scales

    Science.gov (United States)

    Olshevsky, Vyacheslav; Divin, Andrey; Eriksson, Elin; Markidis, Stefano; Lapenta, Giovanni

    2015-07-01

    We use kinetic particle-in-cell and MHD simulations supported by an observational data set to investigate magnetic reconnection in clusters of null points in space plasma. The magnetic configuration under investigation is driven by fast adiabatic flux rope compression that dissipates almost half of the initial magnetic field energy. In this phase powerful currents are excited producing secondary instabilities, and the system is brought into a state of “intermittent turbulence” within a few ion gyro-periods. Reconnection events are distributed all over the simulation domain and energy dissipation is rather volume-filling. Numerous spiral null points interconnected via their spines form null lines embedded into magnetic flux ropes; null point pairs demonstrate the signatures of torsional spine reconnection. However, energy dissipation mainly happens in the shear layers formed by adjacent flux ropes with oppositely directed currents. In these regions radial null pairs are spontaneously emerging and vanishing, associated with electron streams and small-scale current sheets. The number of spiral nulls in the simulation outweighs the number of radial nulls by a factor of 5-10, in accordance with Cluster observations in the Earth's magnetosheath. Twisted magnetic fields with embedded spiral null points might indicate the regions of major energy dissipation for future space missions such as the Magnetospheric Multiscale Mission.

  17. Uncertainty relations, zero point energy and the linear canonical group

    Science.gov (United States)

    Sudarshan, E. C. G.

    1993-01-01

    The close relationship between the zero point energy, the uncertainty relations, coherent states, squeezed states, and correlated states for one mode is investigated. This group-theoretic perspective enables the parametrization and identification of their multimode generalization. In particular the generalized Schroedinger-Robertson uncertainty relations are analyzed. An elementary method of determining the canonical structure of the generalized correlated states is presented.

  18. Establishment of Motion Model for Wave Capture Buoy and Research on Hydrodynamic Performance of Floating-Type Wave Energy Converter

    Directory of Open Access Journals (Sweden)

    Gao Hongtao

    2015-09-01

    Full Text Available Floating-type wave energy converter has the advantages of high wave energy conversion efficiency, strong shock resistance ability in rough sea and stable output power. So it is regarded as a promising energy utilization facility. The research on hydrodynamic performance of wave capture buoys is the precondition and key to the wave energy device design and optimization. A simplified motion model of the buoys in the waves is established. Based on linear wave theory, the equations of motion of buoys are derived according to Newton’s second law. The factors of wave and buoys structural parameters on wave energy absorption efficiency are discussed in the China’s Bohai Sea with short wave period and small wave height. The results show that the main factor which affects the dynamic responses of wave capture buoys is the proximity of the natural frequency of buoys to the wave period. And the incoming wave power takes a backseat role to it at constant wave height. The buoys structural parameters such as length, radius and immersed depth, influence the wave energy absorption efficiency, which play significant factors in device design. The effectiveness of this model is validated by the sea tests with small-sized wave energy devices. The establishment methods of motion model and analysis results are expected to be helpful for designing and manufacturing of floating-type wave energy converter.

  19. Slow-Mode MHD Wave Penetration into a Coronal Null Point due to the Mode Transmission

    Science.gov (United States)

    Afanasyev, Andrey N.; Uralov, Arkadiy M.

    2016-11-01

    Recent observations of magnetohydrodynamic oscillations and waves in solar active regions revealed their close link to quasi-periodic pulsations in flaring light curves. The nature of that link has not yet been understood in detail. In our analytical modelling we investigate propagation of slow magnetoacoustic waves in a solar active region, taking into account wave refraction and transmission of the slow magnetoacoustic mode into the fast one. The wave propagation is analysed in the geometrical acoustics approximation. Special attention is paid to the penetration of waves in the vicinity of a magnetic null point. The modelling has shown that the interaction of slow magnetoacoustic waves with the magnetic reconnection site is possible due to the mode transmission at the equipartition level where the sound speed is equal to the Alfvén speed. The efficiency of the transmission is also calculated.

  20. Increasing durability and lowering the overall cost of wave energy converters using Ultra High Performance Concrete

    DEFF Research Database (Denmark)

    Jepsen, Michael S.; Damkilde, Lars; Hansen, Niels A.

    2013-01-01

    Lowering the overall cost of wave energy converters is a necessity for creating a feasible solution to renewable energy. The design of wave energy converters is in general based on traditional steel design methods. In the design of steel structures subjected to significant dynamical loading...... and a harsh environment issues such fatigue resistance and durability are of major concern. The welded joints in steel structures significantly reduce the fatigue resistance and give a low utilization ratio of the steel material. Furthermore is coating of all exposed steel surfaces a necessity to secure...... as primary material in the design of wave energy converters is a feasible and promising solution, which reduce the overall cost of the structure significantly. This will be illustrated by means of a feasibility study carried out on the Wavestar project, where special attention is pointed at the arm and float...

  1. Turbine Control Strategy using Wave Prediction to Optimise Power Take Off of Overtopping Wave Energy Converters

    DEFF Research Database (Denmark)

    Tedd, James; Knapp, Wilfried; Frigaard, Peter;

    2005-01-01

    This paper presents the control strategy used on Wave Dragon overtopping wave energy converter. The nature of overtopping requires that for optimum performance the water level in the reservoir must be controlled by controlling the turbine outflows. A history of the simulations performed is included...

  2. Thermal effects on parallel resonance energy of whistler mode wave

    Indian Academy of Sciences (India)

    Devendraa Siingh; Shubha Singh; R P Singh

    2006-02-01

    In this short communication, we have evaluated the effect of thermal velocity of the plasma particles on the energy of resonantly interacting energetic electrons with the propagating whistler mode waves as a function of wave frequency and -value for the normal and disturbed magnetospheric conditions. During the disturbed conditions when the magnetosphere is depleted in electron density, the resonance energy of the electron enhances by an order of magnitude at higher latitudes, whereas the effect is small at low latitudes. An attempt is made to explain the enhanced wave activity observed during magnetic storm periods.

  3. MHD wave propagation from the sub-photosphere to the corona in an arcade-shaped magnetic field with a null point

    CERN Document Server

    Santamaria, Irantzu C; Collados, Manuel

    2015-01-01

    The aim of this work is to study the energy transport by means of MHD waves propagating in quiet Sun magnetic topology from layers below the surface to the corona. Upward propagating waves find obstacles, such as the equipartition layer with plasma b=1 and the transition region, and get converted, reflected and refracted. Understanding the mechanisms by which MHD waves can reach the corona can give us information about the solar atmosphere and the magnetic structures. We carry out two-dimensional numerical simulations of wave propagation in a magnetic field structure that consists of two vertical flux tubes separated by an arcade shaped magnetic field. This configuration contains a null point in the corona, that significantly modifies the behaviour of the waves. We describe in detail the wave propagation through the atmosphere under different driving conditions. We also present the spatial distribution of the mean acoustic and magnetic energy fluxes and the spatial distribution of the dominant frequencies in ...

  4. Experimental modelling of the overtopping flow on the Wave Dragon Wave Energy Converter

    Energy Technology Data Exchange (ETDEWEB)

    Parmeggiani, S.; Kofoed, J.P.

    2010-11-15

    The Wave Dragon is a floating slack-moored Wave Energy Converter (WEC) of the overtopping type. Oncoming waves are focused by two wing reflectors towards the ramp of the device, surge-up and overtop into a reservoir placed at a higher level than the surface of the sea. The energy production takes place as the water is led back to the sea through a set of low-head hydro-turbines. After many years of development, Wave Dragon (WD) is now facing the phase of pre-commercial demonstration. In this phase it is very important to be able to use the available data to predict the performances of the device at different scales and locations. A flexible and comprehensive modelling tool is therefore highly required. Wave Dragon produces power through different steps of energy conversion: 1. Primary energy conversion: overtopping - The energy content of the wave (partly in the kinetic and partly in the potential form) is transferred to the device in the form of volumes of water coming into the reservoir. These volumes are stored at a higher level than the surrounding sea, being a stock of potential energy. 2. Secondary energy conversion: turbines - The potential energy stored in the reservoir is transformed into mechanical energy as the water flows back to the sea, activating the lowhead hydro-turbines. 3. Tertiary energy conversion step: generators - The turbines shaft rotation activates the permanent magnet generators, converting mechanical energy into electrical energy. 4. Grid connection and delivery of the power - The electricity produced is delivered to the grid at the right frequency, by means of a frequency converter. The present research is focused on the overtopping. Being the primary energy conversion mechanism of the WD, the overtopping is indeed the stage where the performances of the device are influenced by local conditions and the geometric features of the set-up. This makes it the right step where to account for these features through an accurate modelling

  5. Structural Reliability of Plain Bearings for Wave Energy Converter Applications

    Directory of Open Access Journals (Sweden)

    Simon Ambühl

    2016-02-01

    Full Text Available The levelized cost of energy (LCOE from wave energy converters (WECs needs to be decreased in order to be able to become competitive with other renewable electricity sources. Probabilistic reliability methods can be used to optimize the structure of WECs. Optimization is often performed for critical structural components, like welded details, bolts or bearings. This paper considers reliability studies with a focus on plain bearings available from stock for the Wavestar device, which exists at the prototype level. The Wavestar device is a point absorber WEC. The plan is to mount a new power take-off (PTO system consisting of a discrete displacement cylinder (DDC, which will allow different hydraulic cycles to operate at constant pressure levels. This setup increases the conversion efficiency, as well as decouples the electricity production from the pressure variations within the hydraulic cycle when waves are passing. The new PTO system leads to different load characteristics at the floater itself compared to the actual setup where the turbine/generator is directly coupled to the fluctuating hydraulic pressure within the PTO system. This paper calculates the structural reliability of the different available plain bearings planned to be mounted at the new PTO system based on a probabilistic approach, and the paper gives suggestions for fulfilling the minimal target reliability levels. The considered failure mode in this paper is the brittle fatigue failure of plain bearings. The performed sensitivity analysis shows that parameters defining the initial crack size have a big impact on the resulting reliability of the plain bearing.

  6. Opportunities for shear energy scaling in bulk acoustic wave resonators.

    Science.gov (United States)

    Jose, Sumy; Hueting, Raymond J E

    2014-10-01

    An important energy loss contribution in bulk acoustic wave resonators is formed by so-called shear waves, which are transversal waves that propagate vertically through the devices with a horizontal motion. In this work, we report for the first time scaling of the shear-confined spots, i.e., spots containing a high concentration of shear wave displacement, controlled by the frame region width at the edge of the resonator. We also demonstrate a novel methodology to arrive at an optimum frame region width for spurious mode suppression and shear wave confinement. This methodology makes use of dispersion curves obtained from finite-element method (FEM) eigenfrequency simulations for arriving at an optimum frame region width. The frame region optimization is demonstrated for solidly mounted resonators employing several shear wave optimized reflector stacks. Finally, the FEM simulation results are compared with measurements for resonators with Ta2O5/ SiO2 stacks showing suppression of the spurious modes.

  7. 75 FR 24997 - FPL Energy Point Beach, LLC; Point Beach Nuclear Plant, Units 1 and 2; Environmental Assessment...

    Science.gov (United States)

    2010-05-06

    ... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION FPL Energy Point Beach, LLC; Point Beach Nuclear Plant, Units 1 and 2; Environmental Assessment... Energy Point Beach, LLC (the licensee), for operation of the Point Beach Nuclear Plant, Units 1 and 2...

  8. A Method for EIA Scoping of Wave Energy Converters

    DEFF Research Database (Denmark)

    Margheritini, Lucia; Hansen, Anne Merrild; Frigaard, Peter

    2012-01-01

    During the first decade of the 21st Century the World faces spread concern for global warming caused by rise of green house gasses produced mainly by combustion of fossil fuels. Under this latest spin all renewable energies run parallel in order to achieve sustainable development. Among them wave...... energy has an unequivocal potential and technology is ready to enter the market and contribute to the renewable energy sector. Yet, frameworks and regulations for wave energy development are not fully ready, experiencing a setback caused by lack of understanding of the interaction of the technologies....... This paper presents the development of a classification of wave energy converters that is based on the different impact the technologies are expected to have on the environment. This innovative classification can be used in order to simplify the scoping process for developers and authorities....

  9. Optimal control of oscillation wave energy system using velocity premonition

    Institute of Scientific and Technical Information of China (English)

    CUI; Xiao

    2015-01-01

    Recently ocean wave energy draw much more attention for its widespread,abundant and highly energy flux density properties.Extracting energy from incident wave however,is limited for the random and unstable power input.Motion control for WEC is a promising method to improve the energy absorption and some practical applications are also verified such as latching control.In this paper,an active control strategy is proposed to achieve maximum energy capture.The mathematical description shows that the active control has the characteristic of anti-causal and the wave premonition is necessary for controller design.But the fact of premonition time horizon is still unclear.In this paper,the premonition nature is described mathematically based on hydrodynamic theory.Furthermore,a simulation is also performed to study the impacting of premonition time horizon on WEC’s properties and give a more insightful understanding of WEC active control.

  10. Experimental study of breaking and energy dissipation in surface waves

    Science.gov (United States)

    Ruiz Chavarria, Gerardo; Le Gal, Patrice; Le Bars, Michael

    2014-11-01

    We present an experimental study of the evolution of monochromatic waves produced by a parabolic wave maker. Because of the parabolic shape of the wave front, the waves exhibit spatial focusing and their amplitude dramatically increases over distances of a few wavelengths. Unlike linear waves, the amplitude of the free surface deformation cannot exceed a certain threshold and when this happens the waves break. In order to give a criterion for the appearance of breaking, we calculate the steepness defined as ɛ = H/ λ (where H is the wave height and λ their wavelength) for waves of frequencies in the range 4-10 Hz. We found that wave breaking develops when ɛ attains approximately a value of 0.10. We also evaluate the lost of energy carried by the waves during their breaking by a detailed and accurate measurement of their amplitude using an optical Fourier transform profilometry. G. Ruiz Chavarria acknowledges DGAPA-UNAM by support under Project IN 116312 (Vorticidad y ondas no lineales en fluidos).

  11. The Force of a Tsunami on a Wave Energy Converter

    CERN Document Server

    O'Brien, Laura; Renzi, Emiliano; Dutykh, Denys; Dias, Frédéric

    2012-01-01

    With an increasing emphasis on renewable energy resources, wave power technology is fast becoming a realistic solution. However, the recent tsunami in Japan was a harsh reminder of the ferocity of the ocean. It is known that tsunamis are nearly undetectable in the open ocean but as the wave approaches the shore its energy is compressed creating large destructive waves. The question posed here is whether a nearshore wave energy converter (WEC) could withstand the force of an incoming tsunami. The analytical 3D model of Renzi & Dias (2012) developed within the framework of a linear theory and applied to an array of fixed plates is used. The time derivative of the velocity potential allows the hydrodynamic force to be calculated.

  12. On the dynamics of a novel ocean wave energy converter

    KAUST Repository

    Orazov, B.

    2010-11-01

    Buoy-type ocean wave energy converters are designed to exhibit resonant responses when subject to excitation by ocean waves. A novel excitation scheme is proposed which has the potential to improve the energy harvesting capabilities of these converters. The scheme uses the incident waves to modulate the mass of the device in a manner which amplifies its resonant response. To illustrate the novel excitation scheme, a simple one-degree of freedom model is developed for the wave energy converter. This model has the form of a switched linear system. After the stability regime of this system has been established, the model is then used to show that the excitation scheme improves the power harvesting capabilities by 2565 percent even when amplitude restrictions are present. It is also demonstrated that the sensitivity of the device\\'s power harvesting capabilities to changes in damping becomes much smaller when the novel excitation scheme is used. © 2010 Elsevier Ltd. All rights reserved.

  13. Design Specifications for the Hanstholm WEPTOS Wave Energy Converter

    Directory of Open Access Journals (Sweden)

    Tommy Larsen

    2012-04-01

    Full Text Available The WEPTOS wave energy converter (WEC is a novel device that combines an established and efficient wave energy absorbing mechanism with a smart structure, which can regulate the amount of incoming wave energy and reduce loads in extreme wave conditions. This adjustable A-shaped slack-moored and floating structure absorbs the energy of the waves through a multitude of rotors. The shape of the rotors is based on the renowned Salter’s Duck. On each leg, the rotors pivot around a common axle, through which the rotors transfer the absorbed power to a common power take off system. The study investigates the required capacity of the power take off (PTO system and the structural forces on a WEPTOS WEC prototype, intended for installation at Hanstholm (Denmark, based on large scale experimental tests using a highly realistic laboratory model of the complete device. The results hereof includes the rotational speed and transmitted torque (and hereby power to the PTO system using different PTO control strategies, the impact of fluctuations of the available mechanical power and the effect of limiting the PTO capacity on the annual energy production. Acquisition of structural forces includes mooring forces and structural bending moments in both production and extreme wave conditions, illustrating that the regulation of the angle in the A shape ensures that extreme forces on the structure can be kept in the same order of magnitude as in production conditions.

  14. Experimental Modeling of the Overtopping Flow on the Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Kofoed, Jens Peter; Friis-Madsen, Erik

    2011-01-01

    The Wave Dragon Wave Energy Converter is currently facing a precommercial phase. At this stage of development a reliable overtopping model is highly required, in order to predict the performance of the device at possible deployment locations. A model formulation derived for an overtopping device...... with general geometry has been used so far. The paper presents an updated formulation drawn through the tank testing of a scaled model the Wave Dragon. The sensitivity analysis of the main features influencing the overtopping flow led to an updated model formulation which can be specifically suited...... for the Wave Dragon....

  15. Experimental Modeling of the Overtopping Flow on the Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Kofoed, Jens Peter; Friis-Madsen, Erik

    2011-01-01

    The Wave Dragon Wave Energy Converter is currently facing a precommercial phase. At this stage of development a reliable overtopping model is highly required, in order to predict the performance of the device at possible deployment locations. A model formulation derived for an overtopping device...... with general geometry has been used so far. The paper presents an updated formulation drawn through the tank testing of a scaled model the Wave Dragon. The sensitivity analysis of the main features influencing the overtopping flow led to an updated model formulation which can be specifically suited...... for the Wave Dragon....

  16. Wave energy budget analysis in the Earth's radiation belts uncovers a missing energy

    National Research Council Canada - National Science Library

    Artemyev, A V; Agapitov, O V; Mourenas, D; Krasnoselskikh, V V; Mozer, F S

    2015-01-01

    .... Here, we report an analysis of 10-year Cluster data, statistically evaluating the full wave energy budget in the Earth's magnetosphere, revealing that a significant fraction of the energy corresponds...

  17. Measurements of Overtopping Flow Time Series on the Wave Dragon, Wave Energy Converter

    DEFF Research Database (Denmark)

    Tedd, James; Kofoed, Jens Peter

    2009-01-01

    A study of overtopping flow series on the Wave Dragon prototype, a low crested device designed to maximise flow, in a real sea, is presented. This study aims to fill the gap in the literature on time series of flow overtopping low crested structures. By comparing to a simulated flow the character......A study of overtopping flow series on the Wave Dragon prototype, a low crested device designed to maximise flow, in a real sea, is presented. This study aims to fill the gap in the literature on time series of flow overtopping low crested structures. By comparing to a simulated flow...... the characteristics of the overtopping flow are discussed and the simulation algorithm is tested. Measured data is shown from a storm build up in October 2006, from theWave Dragon prototype situated in an inland sea in Northern Denmark. This wave energy converter extracts energy from the waves, by funnelling them...

  18. Wave propagation of spectral energy content in a granular chain

    Science.gov (United States)

    Shrivastava, Rohit Kumar; Luding, Stefan

    2017-06-01

    A mechanical wave is propagation of vibration with transfer of energy and momentum. Understanding the spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through inhomogeneous materials like soil. The study of these properties is aimed at modeling wave propagation for oil, mineral or gas exploration (seismic prospecting) or non-destructive testing of the internal structure of solids. The focus is on the total energy content of a pulse propagating through an idealized one-dimensional discrete particle system like a mass disordered granular chain, which allows understanding the energy attenuation due to disorder since it isolates the longitudinal P-wave from shear or rotational modes. It is observed from the signal that stronger disorder leads to faster attenuation of the signal. An ordered granular chain exhibits ballistic propagation of energy whereas, a disordered granular chain exhibits more diffusive like propagation, which eventually becomes localized at long time periods. For obtaining mean-field macroscopic/continuum properties, ensemble averaging has been used, however, such an ensemble averaged spectral energy response does not resolve multiple scattering, leading to loss of information, indicating the need for a different framework for micro-macro averaging.

  19. Wave propagation of spectral energy content in a granular chain

    Directory of Open Access Journals (Sweden)

    Shrivastava Rohit Kumar

    2017-01-01

    Full Text Available A mechanical wave is propagation of vibration with transfer of energy and momentum. Understanding the spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through inhomogeneous materials like soil. The study of these properties is aimed at modeling wave propagation for oil, mineral or gas exploration (seismic prospecting or non-destructive testing of the internal structure of solids. The focus is on the total energy content of a pulse propagating through an idealized one-dimensional discrete particle system like a mass disordered granular chain, which allows understanding the energy attenuation due to disorder since it isolates the longitudinal P-wave from shear or rotational modes. It is observed from the signal that stronger disorder leads to faster attenuation of the signal. An ordered granular chain exhibits ballistic propagation of energy whereas, a disordered granular chain exhibits more diffusive like propagation, which eventually becomes localized at long time periods. For obtaining mean-field macroscopic/continuum properties, ensemble averaging has been used, however, such an ensemble averaged spectral energy response does not resolve multiple scattering, leading to loss of information, indicating the need for a different framework for micro-macro averaging.

  20. Reducing Zero-point Systematics in Dark Energy Supernova Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Faccioli, Lorenzo; Kim, Alex G; Miquel, Ramon; Bernstein, Gary; Bonissent, Alain; Brown, Matthew; Carithers, William; Christiansen, Jodi; Connolly, Natalia; Deustua, Susana; Gerdes, David; Gladney, Larry; Kushner, Gary; Linder, Eric; McKee, Shawn; Mostek, Nick; Shukla, Hemant; Stebbins, Albert; Stoughton, Chris; Tucker, David

    2011-04-01

    We study the effect of filter zero-point uncertainties on future supernova dark energy missions. Fitting for calibration parameters using simultaneous analysis of all Type Ia supernova standard candles achieves a significant improvement over more traditional fit methods. This conclusion is robust under diverse experimental configurations (number of observed supernovae, maximum survey redshift, inclusion of additional systematics). This approach to supernova fitting considerably eases otherwise stringent mission cali- bration requirements. As an example we simulate a space-based mission based on the proposed JDEM satellite; however the method and conclusions are general and valid for any future supernova dark energy mission, ground or space-based.

  1. Dark energy and normalization of the cosmological wave function

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Peng [Sun Yat-Sen University, School of Astronomy and Space Science, Guangzhou (China); Huang, Yue; Li, Nan [Institute of Theoretical Physics, Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Beijing (China); Kavli Institute for Theoretical Physics China, Chinese Academy of Sciences, Beijing (China); Li, Miao [Sun Yat-Sen University, School of Astronomy and Space Science, Guangzhou (China); Institute of Theoretical Physics, Chinese Academy of Sciences, State Key Laboratory of Theoretical Physics, Beijing (China)

    2016-08-15

    Dark energy is investigated from the perspective of quantum cosmology. It is found that, together with an appropriate normal ordering factor q, only when there is dark energy can the cosmological wave function be normalized. This interesting observation may require further attention. (orig.)

  2. Designing and Testing Composite Energy Storage Systems for Regulating the Outputs of Linear Wave Energy Converters

    Directory of Open Access Journals (Sweden)

    Zanxiang Nie

    2017-01-01

    Full Text Available Linear wave energy converters generate intrinsically intermittent power with variable frequency and amplitude. A composite energy storage system consisting of batteries and super capacitors has been developed and controlled by buck-boost converters. The purpose of the composite energy storage system is to handle the fluctuations and intermittent characteristics of the renewable source, and hence provide a steady output power. Linear wave energy converters working in conjunction with a system composed of various energy storage devices, is considered as a microsystem, which can function in a stand-alone or a grid connected mode. Simulation results have shown that by applying a boost H-bridge and a composite energy storage system more power could be extracted from linear wave energy converters. Simulation results have shown that the super capacitors charge and discharge often to handle the frequent power fluctuations, and the batteries charge and discharge slowly for handling the intermittent power of wave energy converters. Hardware systems have been constructed to control the linear wave energy converter and the composite energy storage system. The performance of the composite energy storage system has been verified in experiments by using electronics-based wave energy emulators.

  3. Stochastic Rating of Storage Systems in Isolated Networks with Increasing Wave Energy Penetration

    Directory of Open Access Journals (Sweden)

    Elisabetta Tedeschi

    2013-05-01

    Full Text Available The future success of wave energy in the renewable energy mix depends on the technical advancements of the specific components and systems, on the grid access availability and, ultimately, on the economical profitability of the investment. Small and remote islands represent an ideal framework for wave energy exploitation, due both to resource availability and to the current high cost of electricity that mostly relies on diesel generation. Energy storage can be the enabling technology to match the intermittent power generation from waves to the energy needs of the local community. In this paper real data from La Palma, in the Canary Islands, are used as a basis for the considered test case. As a first step the study quantifies the expected power production from Wave Energy Converter (WEC arrays, based on data from the Lifesaver point absorber developed by Fred. Olsen. Then, a stochastic optimization approach is applied to evaluate the convenience of energy storage introduction for reducing the final cost of energy and to define the corresponding optimal rating of the storage devices.

  4. User guide – COE Calculation Tool for Wave Energy Converters

    DEFF Research Database (Denmark)

    Chozas, Julia Fernandez; Kofoed, Jens Peter; Jensen, Niels Ejner Helstrup

    Aalborg University together with Energinet.dk and Julia F. Chozas Consulting Engineer, have released a freely available online spreadsheet to evaluate the Levelised Cost of Energy (LCOE) for wave energy projects. The open-access tool calculates the LCOE based on the power production of a Wave...... Energy Converter (WEC) at a particular location. Production data may derive from laboratory testing, numerical modelling or from sea trials. The tool has been developed as a transparent and simple model that evaluates WEC’s economic feasibility in a range of locations, while scaling WEC’s features...

  5. Wave-current interactions at the FloWave Ocean Energy Research Facility

    Science.gov (United States)

    Noble, Donald; Davey, Thomas; Steynor, Jeffrey; Bruce, Tom; Smith, Helen; Kaklis, Panagiotis

    2015-04-01

    Physical scale model testing is an important part of the marine renewable energy development process, allowing the study of forces and device behaviour in a controlled environment prior to deployment at sea. FloWave is a new state-of-the-art ocean energy research facility, designed to provide large scale physical modelling services to the tidal and wave sector. It has the unique ability to provide complex multi-directional waves that can be combined with currents from any direction in the 25m diameter circular tank. The facility is optimised for waves around 2s period and 0.4m height, and is capable of generating currents upwards of 1.6m/s. This offers the ability to model metocean conditions suitable for most renewable energy devices at a typical scale of between 1:10 and 1:40. The test section is 2m deep, which can be classed as intermediate-depth for most waves of interest, thus the full dispersion equation must be solved as the asymptotic simplifications do not apply. The interaction between waves and currents has been studied in the tank. This has involved producing in the tank sets of regular waves, focussed wave groups, and random sea spectra including multi-directional sea states. These waves have been both inline-with and opposing the current, as well as investigating waves at arbitrary angles to the current. Changes in wave height and wavelength have been measured, and compared with theoretical results. Using theoretical wave-current interaction models, methods have been explored to "correct" the wave height in the central test area of the tank when combined with a steady current. This allows the wave height with current to be set equal to that without a current. Thus permitting, for example, direct comparison of device motion response between tests with and without current. Alternatively, this would also permit a specific wave height and current combination to be produced in the tank, reproducing recorded conditions at a particular site of interest. The

  6. CFD supported examination of buoy design for wave energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz, Nadir; Trapp, Geoffrey E.; Gagan, Scott M.; Emmerich, Timothy R. [Department of Mechanical Engineering, New Mexico Institute of Mining and Technology (United States)], e-mail: nadir@nmt.edu, email: gtrapp@nmt.edu, email: sgag01@nmt.edu, email: temmeric@nmt.edu

    2011-07-01

    The work presented in this paper investigates an oscillating buoy power device (OD) as a potential wave energy converter. The wave interacts with the buoy, which is connected to a mechanical device which oscillates and converts spring force into mechanical power. For validation purposes, ellipsoidal buoy shapes of the five aspect ratios are used in this report as OD devices which are excited under the same wave conditions to validate the computational fluid dynamics (CFD) model against experimental data available in the literature. The analysis was performed using a Flow-3d CFD software package. Comparisons are made and results are presented based on buoy displacements which can be related to energy produced by the buoys. The aspect ratio approaching 1:1:1 (sphere) is found to produce the maximum displacement and consequently the highest possible energy conversion. The paper also discusses whether a flat circular plate shape buoy would capture 50% of the possible energy by comparison with the spherical buoy.

  7. Formation of determinate fields of intensity and polarization in the vicinity of specified point basing on three-wave interference

    Science.gov (United States)

    Sakhnovskyj, Mykhajlo Y.; Tymochko, Bogdan M.; Rudeichuk, Volodymyr M.; Dominikov, Mickolay M.

    2015-11-01

    The polarization structure of a field at the superposition of two plain orthogonally linear polarized coherent light waves with the referent wave with some state of polarization is considered. It is shown, that with the help of referent wave zero intensity could be created in any point of the observation plane, if the state of polarization of the referent wave coincides with the state of polarization in this point without the referent wave, and the electrical vector of the referent wave oscillates in counterphase with the electrical vector of the superposition of two first waves.

  8. Energy dissipation in magnetic null points at kinetic scales

    OpenAIRE

    Olshevsky, Vyacheslav; Divin, Andrey; Eriksson, Elin; Markidis, Stefano; Lapenta, Giovanni

    2015-01-01

    We use kinetic particle-in-cell and MHD simulations supported by an observational data set to investigate magnetic reconnection in clusters of null points in space plasma. The magnetic configuration under investigation is driven by fast adiabatic flux rope compression that dissipates almost half of the initial magnetic field energy. In this phase powerful currents are excited producing secondary instabilities, and the system is brought into a state of "intermittent turbulence" within a few io...

  9. Point Lepreau refurbishment and energy outlook in New Brunswick

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, B. [NB Power, Fredericton, New Brunswick (Canada)

    2011-07-01

    This paper is about Point Lepreau refurbishment and energy outlook in New Brunswick. The mission of New Brunswick Power is to ensure the safety of workers, public and the environment, executing planned outages on time and on budget, and in a quality manner, operating plants more efficiently with a high level of reliability, meeting regulatory commitments and completing the refurbishment project and returning the station to service.

  10. Attitude pointing enhancement for combined energy and attitude control system

    Science.gov (United States)

    Varatharajoo, Renuganth; Tech Wooi, Choo; Mailah, Musa

    2011-06-01

    This paper extends the previous works that appeared in Acta Astronautica. An approach that incorporates the Active Force Control (AFC) technique into a conventional Proportional-Derivative (PD) controller is proposed for a 50 kg small satellite. Numerical treatments are performed to validate the effectiveness of AFC. The attitude control capability of the combined energy and attitude control system (CEACS) is expected to improve. The result shows an important attitude pointing enhancement for the CEACS attitude control task.

  11. Stress Points to Energy Saving and Environmental Protection

    Institute of Scientific and Technical Information of China (English)

    Fang Weizhong; Jin Wen

    2007-01-01

    @@ GDP growth of 10.5% in 2006 can't be admired without analysis. The growth of 2.5 percentage points beyond the state's plan was achieved on the costs that energy consumption remained at a high increase rate of 11% and the total discharge amount of main pollutants increased but decreased. To balance out the gain against the loss,the gain is unlikely to outweigh the loss.

  12. Energy transfer from lower energy to higher-energy electrons mediated by whistler waves in the radiation belts

    Science.gov (United States)

    Shklyar, D. R.

    2017-01-01

    We study the problem of energy exchange between waves and particles, which leads to energization of the latter, in an unstable plasma typical of the radiation belts. The ongoing Van Allen Probes space mission brought this problem among the most discussed in space physics. A free energy which is present in an unstable plasma provides the indispensable condition for energy transfer from lower energy particles to higher-energy particles via resonant wave-particle interaction. This process is studied in detail by the example of electron interactions with whistler mode wave packets originated from lightning-induced emission. We emphasize that in an unstable plasma, the energy source for electron energization is the energy of other particles, rather than the wave energy as is often assumed. The way by which the energy is transferred from lower energy to higher-energy particles includes two processes that operate concurrently, in the same space-time domain, or sequentially, in different space-time domains, in which a given wave packet is located. In the first process, one group of resonant particles gives the energy to the wave. The second process consists in wave absorption by another group of resonant particles, whose energy therefore increases. We argue that this mechanism represents an efficient means of electron energization in the radiation belts.

  13. Solar energy converter using surface plasma waves

    Science.gov (United States)

    Anderson, L. M. (Inventor)

    1984-01-01

    Sunlight is dispersed over a diffraction grating formed on the surface of a conducting film on a substrate. The angular dispersion controls the effective grating period so that a matching spectrum of surface plasmons is excited for parallel processing on the conducting film. The resulting surface plasmons carry energy to an array of inelastic tunnel diodes. This solar energy converter does not require different materials for each frequency band, and sunlight is directly converted to electricity in an efficient manner by extracting more energy from the more energetic photons.

  14. Comparison study on spherical wave superposition method and spherical wave source boundary point method for realizing nearfield acoustic holography

    Institute of Scientific and Technical Information of China (English)

    BI Chuanxing; CHEN Xinzhao; ZHOU Rong; CHEN Jian

    2005-01-01

    In the light of the concept of spherical wave source, the theoretical model of nearfield acoustic holography (NAH) based on the spherical wave superposition method (SWSM), including reconstruction of expansion coefficients, prediction of acoustic field, error sensitivity analysis, regularization method and a searching method with dual measurement surfaces for determining the optimal number of expansion terms, is established. Subsequently, the spherical wave source boundary point method (SWSBPM) and its application in the NAH are introduced briefly. Considering the similarity of the SWSM and the SWSBPM for realizing the NAH, they are compared. The similarities and differences of the two methods are illuminated by a rigorous mathematical justification and two experiments on a single source and two coherent sources in the semi-free acoustic field. And, the superiority of the NAH based on the SWSBPM is demonstrated.

  15. Are Wave and Tidal Energy Plants New Green Technologies?

    Science.gov (United States)

    Douziech, Mélanie; Hellweg, Stefanie; Verones, Francesca

    2016-07-19

    Wave and tidal energy plants are upcoming, potentially green technologies. This study aims at quantifying their various potential environmental impacts. Three tidal stream devices, one tidal range plant and one wave energy harnessing device are analyzed over their entire life cycles, using the ReCiPe 2008 methodology at midpoint level. The impacts of the tidal range plant were on average 1.6 times higher than the ones of hydro-power plants (without considering natural land transformation). A similar ratio was found when comparing the results of the three tidal stream devices to offshore wind power plants (without considering water depletion). The wave energy harnessing device had on average 3.5 times higher impacts than offshore wind power. On the contrary, the considered plants have on average 8 (wave energy) to 20 (tidal stream), or even 115 times (tidal range) lower impact than electricity generated from coal power. Further, testing the sensitivity of the results highlighted the advantage of long lifetimes and small material requirements. Overall, this study supports the potential of wave and tidal energy plants as alternative green technologies. However, potential unknown effects, such as the impact of turbulence or noise on marine ecosystems, should be further explored in future research.

  16. Local energy decay for linear wave equations with variable coefficients

    Science.gov (United States)

    Ikehata, Ryo

    2005-06-01

    A uniform local energy decay result is derived to the linear wave equation with spatial variable coefficients. We deal with this equation in an exterior domain with a star-shaped complement. Our advantage is that we do not assume any compactness of the support on the initial data, and its proof is quite simple. This generalizes a previous famous result due to Morawetz [The decay of solutions of the exterior initial-boundary value problem for the wave equation, Comm. Pure Appl. Math. 14 (1961) 561-568]. In order to prove local energy decay, we mainly apply two types of ideas due to Ikehata-Matsuyama [L2-behaviour of solutions to the linear heat and wave equations in exterior domains, Sci. Math. Japon. 55 (2002) 33-42] and Todorova-Yordanov [Critical exponent for a nonlinear wave equation with damping, J. Differential Equations 174 (2001) 464-489].

  17. Study Pelamis system to capture energy of ocean wave

    CERN Document Server

    Gobato, Ricardo; Fedrigo, Desire Francine Gobato

    2015-01-01

    Over the years, energy has become vital for humans, enabling us to comfort, leisure, mobility and other factors. The quest for cheap energy sources, renewable and clean has grown in recent years, mainly for the reduction of effects that comes degrading nature, allowing scientists and engineers to search for new technologies. Many energy sources have been researched for proper funding where some stand out for their ease of obtaining, by other low cost and others by being renewable. The main objective of this work is to study one of these energy sources - wave energy, whose capture is still in development. This energy comes from the waves of the sea and is 100% renewable and with minimal environmental impact when compared to hydro, nuclear, coal, thermal, etc. The system studied here is the Pelamis system.

  18. Selection of Design Power of Wave Energy Converters Based on Wave Basin Experiments

    DEFF Research Database (Denmark)

    Martinelli, L.; Zanuttigh, B.; Kofoed, Jens Peter

    2011-01-01

    of the measured efficiency; description of the energy production by means of a function of the design capacity; application of a simple formula for cost benefit analysis. The analyses here proposed are based on the experimental results of 3D tests on two floating wave energy devices, named LEANCON and DEXA...

  19. Smart metacomposite-based systems for transient elastic wave energy harvesting

    Science.gov (United States)

    Yi, K.; Monteil, M.; Collet, M.; Chesne, S.

    2017-03-01

    In this paper, novel harvesting systems are proposed and studied to obtain enhanced energy from transient waves. Each of these systems contains a piezo-lens to focus waves and a harvester to yield energy from the induced focused waves. The piezo-lens comprises a host plate and piezoelectric patches bonded on the plate surfaces. The piezoelectric patches are shunted with negative capacitance (NC) circuits in order to control the spatial variation of the effective refractive index inside the piezo-lens domain. The harvester is placed at the designed focal point of the piezo-lens, two different synchronized switch harvesting on inductor (SSHI) based harvesters are analyzed in the studies. Corrected reduced models are developed to predict the transient responses of the harvesting systems. The performances of the systems incorporating SSHI-based harvesters in transient wave energy harvesting are studied and compared with the system using a standard DC harvester. The focusing effect of the piezo-lens on transient waves and its capability to improve the harvested energy are verified. Since the NC circuits are active elements, an energy balance analysis is performed. Applicability of the harvesting systems is also discussed.

  20. The SSG Wave Energy Converter: Performance, Status and Recent Developments

    Directory of Open Access Journals (Sweden)

    Mariano Buccino

    2012-01-01

    Full Text Available The Sea-wave Slot-cone Generator (SSG is a Wave Energy Converter based on the wave overtopping principle; it employs several reservoirs placed on top of each other, in which the energy of incoming waves is stored as potential energy. Then, the captured water runs through turbines for electricity production. The system works under a wide spectrum of different wave conditions, giving a high overall efficiency. It can be suitable for shoreline and breakwater applications and presents particular advantages, such as sharing structure costs, availability of grid connection and recirculation of water inside the harbor, as the outlet of the turbines is on the rear part of the system. Recently, plans for the SSG pilot installations are in progress at the Svaaheia site (Norway, the port of Hanstholm (Denmark and the port of Garibaldi (Oregon, USA. In the last-mentioned two projects, the Sea-wave Slot-cone Generator technology is integrated into the outer harbor breakwater and jetty reconstruction projects. In the last years extensive studies have been performed on the hydraulic and the structural response of this converter, with the aim of optimizing the design process. The investigations have been conducted by physical model tests and numerical simulations and many results have been published on both conference proceedings and journals. The main scope of this paper is reviewing the most significant findings, to provide the reader with an organic overview on the present status of knowledge.

  1. On the asymptotic evolution of finite energy Airy wave functions.

    Science.gov (United States)

    Chamorro-Posada, P; Sánchez-Curto, J; Aceves, A B; McDonald, G S

    2015-06-15

    In general, there is an inverse relation between the degree of localization of a wave function of a certain class and its transform representation dictated by the scaling property of the Fourier transform. We report that in the case of finite energy Airy wave packets a simultaneous increase in their localization in the direct and transform domains can be obtained as the apodization parameter is varied. One consequence of this is that the far-field diffraction rate of a finite energy Airy beam decreases as the beam localization at the launch plane increases. We analyze the asymptotic properties of finite energy Airy wave functions using the stationary phase method. We obtain one dominant contribution to the long-term evolution that admits a Gaussian-like approximation, which displays the expected reduction of its broadening rate as the input localization is increased.

  2. Licensing and Environmental Issues of Wave Energy Projects

    DEFF Research Database (Denmark)

    Neumann, Frank; Tedd, James; Prado, Miguel;

    2006-01-01

    The major non-technical barrier for large-scale wave energy implementation is the wide range of licensing issues and potential environmental concerns, in addition to significant National/regional differences in licensing procedures and permit requirements. Whereas some pilot plants have had...... a special standing or facilitated access to operating licenses due to their experimental character, the move of wave energy projects towards commercial applications implies complex procedures for obtaining licenses both with respect to the construction and deployment and operation phases, as well....... Different National settings and traditional use of ocean space, as well as different levels of advance in terms of legislation and procedural effectiveness make it extremely difficult to set out implementation strategies for ocean wave energy technologies. The paper includes a brief experience review from...

  3. Synergies for a Wave-Wind Energy Concept

    DEFF Research Database (Denmark)

    Pérez-Collazo, Carlos; Jakobsen, Morten Møller; Chozas, Julia Fernandez

    2013-01-01

    installation costs relative to separate installations. Therefore, new hybrid or multiplatform solutions are being developed. Approach This work is focused on the integration of Wave Energy Converters (WECs) into offshore wind farms. Furthermore, the sustainable development of both offshore wind and wave...... into the positive synergies when offshore wind and wave energy technologies share the same marine space. Among that ones are: shared cost; a smoothing power output; and shielding effects of WECs over the offshore wind farm, which contribute to increase the weather windows for operation and maintenance. Secondly......, this work outlines the risks and challenges that arise when combining these energies. To some extent WECs increase the uncertainty of the project, leading to a higher project cost and an increase the associated financial risk. In third place three case studies are proposed to illustrate different...

  4. Energy flow characteristics of vector X-Waves

    KAUST Repository

    Salem, Mohamed

    2011-01-01

    The vector form of X-Waves is obtained as a superposition of transverse electric and transverse magnetic polarized field components. It is shown that the signs of all components of the Poynting vector can be locally changed using carefully chosen complex amplitudes of the transverse electric and transverse magnetic polarization components. Negative energy flux density in the longitudinal direction can be observed in a bounded region around the centroid; in this region the local behavior of the wave field is similar to that of wave field with negative energy flow. This peculiar energy flux phenomenon is of essential importance for electromagnetic and optical traps and tweezers, where the location and momenta of microand nanoparticles are manipulated by changing the Poynting vector, and in detection of invisibility cloaks. © 2011 Optical Society of America.

  5. Offshore energy structures for wind power, wave energy and hybrid marine platforms

    CERN Document Server

    Karimirad, Madjid

    2014-01-01

    This book provides all the key information needed to design offshore structures for renewable energy applications successfully. Suitable for practicing engineers and students, the author conveys design principles and best practices in a clear, concise manner, focusing on underlying physics while eschewing complicated mathematical detail. The text connects underlying scientific theory with industry standards and practical implementation issues for offshore wind turbines, wave energy converters and current turbines. Combined concepts such as wave-wind energy platforms are discussed, as well. Cov

  6. Measurements of radiated elastic wave energy from dynamic tensile cracks

    Science.gov (United States)

    Boler, Frances M.

    1990-01-01

    The role of fracture-velocity, microstructure, and fracture-energy barriers in elastic wave radiation during a dynamic fracture was investigated in experiments in which dynamic tensile cracks of two fracture cofigurations of double cantilever beam geometry were propagating in glass samples. The first, referred to as primary fracture, consisted of fractures of intact glass specimens; the second configuration, referred to as secondary fracture, consisted of a refracture of primary fracture specimens which were rebonded with an intermittent pattern of adhesive to produce variations in fracture surface energy along the crack path. For primary fracture cases, measurable elastic waves were generated in 31 percent of the 16 fracture events observed; the condition for radiation of measurable waves appears to be a local abrupt change in the fracture path direction, such as occurs when the fracture intersects a surface flaw. For secondary fractures, 100 percent of events showed measurable elastic waves; in these fractures, the ratio of radiated elastic wave energy in the measured component to fracture surface energy was 10 times greater than for primary fracture.

  7. Model Predictive Control of Buoy Type Wave Energy Converter

    DEFF Research Database (Denmark)

    Soltani, Mohsen; Sichani, Mahdi Teimouri; Mirzaei, Mahmood

    2014-01-01

    The paper introduces the Wavestar wave energy converter and presents the implementation of model predictive controller that maximizes the power generation. The ocean wave power is extracted using a hydraulic electric generator which is connected to an oscillating buoy. The power generator is an a....... This approach is then taken into account and an MPC controller is designed for a model WEC and implemented on a numerical example. Further, the power outtake of this controller is compared to the optimal controller as an indicator of the performance of the designed controller.......The paper introduces the Wavestar wave energy converter and presents the implementation of model predictive controller that maximizes the power generation. The ocean wave power is extracted using a hydraulic electric generator which is connected to an oscillating buoy. The power generator...... is an additive device attached to the buoy which may include damping, stiffness or similar terms hence will affect the dynamic motion of the buoy. Therefore such a device can be seen as a closed-loop controller. The objective of the wave energy converter is to harvest as much energy from sea as possible...

  8. Identification and quantification of potential wave energy in the coast of Atlántico state in Colombia

    Directory of Open Access Journals (Sweden)

    Jaime Pérez-Zapata

    2017-06-01

    Full Text Available This paper describes the progress regarding the identification and quantification of potential wave energy in Atlántico state coast. The used methodology will serve as a starting point to establish the energetic potential in Colombia in this energy. The theoretical energetic potential estimated at the near shore in the Atlantic coast waves is approximately 1107 MW and this was possible with data that has been collected and processed since January 2016. We applied equations that take into account variables such as: significant wave height, period, sea water density, temperature and wind speed in the area. Also it is shown the progress of the near shore system design for the verification of the wave energetic potential consisting of a device which transforms kinetic energy of the sea waves into gravitational potential energy that is going to be used to move an alternating current generator.

  9. Thermodynamics of relativistic quantum fields: extracting energy from gravitational waves

    CERN Document Server

    Bruschi, David Edward

    2016-01-01

    We investigate the quantum thermodynamical properties of localised relativistic quantum fields that can be used as quantum thermal machines. We study the efficiency and power of energy transfer between the classical degrees of freedom, such as the energy input due to motion or to an impinging gravitational wave, and the excitations of the confined quantum field. We find that the efficiency of energy transfer depends dramatically on the input initial state of the system. Furthermore, we investigate the ability to extract the energy and to store it in a battery. This process is inefficient in optical cavities but is significantly enhanced when employing trapped Bose Einstein Condensates. Finally, we apply our techniques to a setup where an impinging gravitational wave excites the phononic modes of a Bose Einstein Condensate. We find that, in this case, the amount of energy transfer to the phonons increases with time and quickly approaches unity. These results suggest that, in the future, it might be possible to...

  10. Methodological demonstration of laser beam pointing control for space gravitational wave detection missions.

    Science.gov (United States)

    Dong, Yu-Hui; Liu, He-Shan; Luo, Zi-Ren; Li, Yu-Qiong; Jin, Gang

    2014-07-01

    In space laser interferometer gravitational wave (G.W.) detection missions, the stability of the laser beam pointing direction has to be kept at 10 nrad/√Hz. Otherwise, the beam pointing jitter noise will dominate the noise budget and make the detection of G.W. impossible. Disturbed by the residue non-conservative forces, the fluctuation of the laser beam pointing direction could be a few μrad/√Hz at frequencies from 0.1 mHz to 10 Hz. Therefore, the laser beam pointing control system is an essential requirement for those space G.W. detection missions. An on-ground test of such beam pointing control system is performed, where the Differential Wave-front Sensing technique is used to sense the beams pointing jitter. An active controlled steering mirror is employed to adjust the beam pointing direction to compensate the jitter. The experimental result shows that the pointing control system can be used for very large dynamic range up to 5 μrad. At the interested frequencies of space G.W. detection missions, between 1 mHz and 1 Hz, beam pointing stability of 6 nrad/√Hz is achieved.

  11. Structural Reliability of Plain Bearings for Wave Energy Converter Applications

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kramer, Morten Mejlhede; Sørensen, John Dalsgaard

    2016-01-01

    The levelized cost of energy (LCOE) from wave energy converters (WECs) needs to be decreased in order to be able to become competitive with other renewable electricity sources. Probabilistic reliability methods can be used to optimize the structure of WECs. Optimization is often performed...... the hydraulic cycle when waves are passing. The new PTO system leads to different load characteristics at the floater itself compared to the actual setup where the turbine/generator is directly coupled to the fluctuating hydraulic pressure within the PTO system. This paper calculates the structural reliability...

  12. Reliability-Based Structural Optimization of Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kramer, Morten; Sørensen, John Dalsgaard

    2014-01-01

    More and more wave energy converter (WEC) concepts are reaching prototype level. Once the prototype level is reached, the next step in order to further decrease the levelized cost of energy (LCOE) is optimizing the overall system with a focus on structural and maintenance (inspection) costs......, as well as on the harvested power from the waves. The target of a fully-developed WEC technology is not maximizing its power output, but minimizing the resulting LCOE. This paper presents a methodology to optimize the structural design of WECs based on a reliability-based optimization problem...

  13. Foam drainage wave coalescing and its energy evolution

    Institute of Scientific and Technical Information of China (English)

    SUN QiCheng; HUANG Jin; WANG GuangQian

    2008-01-01

    Liquid foam is a dense packing of gas bubbles in a small amount of surfactant solution. Liquid drains out of foams until equilibrium is reached due to the compromise between gravity and capillarity, which greatly affects the stability of foam. Based on a series of work on foam structure and drainage we conducted previously, this paper reports the results on coalescence of an original forced drainage wave at a low flow rate with subsequent drainage waves with higher flow rates. The evolutions of vis-cous energy and surface energy during the process of coalescence are theoretically analyzed.

  14. Modeling and Simulation of a Wave Energy Converter INWAVE

    OpenAIRE

    Seung Kwan Song; Yong Jun Sung; Jin Bae Park

    2017-01-01

    INGINE Inc. developed its own wave energy converter (WEC) named INWAVE and has currently installed three prototype modules in Jeju Island, Korea. This device is an on-shore-type WEC that consists of a buoy, pulleys fixed to the sea-floor and a power take off module (PTO). Three ropes are moored tightly on the bottom of the buoy and connected to the PTO via the pulleys, which are moving back and forth according to the motion of the buoy. Since the device can harness wave energy from all six de...

  15. Experimental Investigation of Irregular Wave Cancellation Using a Cycloidal Wave Energy Converter

    Science.gov (United States)

    2012-07-01

    CycWEC consists of one or more hydrofoils attached equidistant to a shaft that is aligned parallel to the incoming waves. The entire device is fully sub...300 scale wave tunnel experiment. A CycWEC consists of one or more hydrofoils attached equidistant to a shaft that is aligned parallel to the incoming...Prescribed by ANSI Std Z39-18 g Gravity constant, 9.81[m/s2] t Time [s] λ Wavelength [m] R = 60mm Wave Energy Converter Radius [m] c = 50mm Hydrofoil Chord

  16. Hydrodynamic analysis and shape optimization for vertical axisymmetric wave energy converters

    Science.gov (United States)

    Zhang, Wan-chao; Liu, Heng-xu; Zhang, Liang; Zhang, Xue-wei

    2016-12-01

    The absorber is known to be vertical axisymmetric for a single-point wave energy converter (WEC). The shape of the wetted surface usually has a great influence on the absorber's hydrodynamic characteristics which are closely linked with the wave power conversion ability. For complex wetted surface, the hydrodynamic coefficients have been predicted traditionally by hydrodynamic software based on the BEM. However, for a systematic study of various parameters and geometries, they are too multifarious to generate so many models and data grids. This paper examines a semi-analytical method of decomposing the complex axisymmetric boundary into several ring-shaped and stepped surfaces based on the boundary discretization method (BDM) which overcomes the previous difficulties. In such case, by using the linear wave theory based on eigenfunction expansion matching method, the expressions of velocity potential in each domain, the added mass, radiation damping and wave excitation forces of the oscillating absorbers are obtained. The good astringency of the hydrodynamic coefficients and wave forces are obtained for various geometries when the discrete number reaches a certain value. The captured wave power for a same given draught and displacement for various geometries are calculated and compared. Numerical results show that the geometrical shape has great effect on the wave conversion performance of the absorber. For absorbers with the same outer radius and draught or displacement, the cylindrical type shows fantastic wave energy conversion ability at some given frequencies, while in the random sea wave, the parabolic and conical ones have better stabilization and applicability in wave power conversion.

  17. Use of Finite Point Method for Wave Propagation in Nonhomogeneous Unbounded Domains

    Directory of Open Access Journals (Sweden)

    S. Moazam

    2015-01-01

    Full Text Available Wave propagation in an unbounded domain surrounding the stimulation resource is one of the important issues for engineers. Past literature is mainly concentrated on the modelling and estimation of the wave propagation in partially layered, homogeneous, and unbounded domains with harmonic properties. In this study, a new approach based on the Finite Point Method (FPM has been introduced to analyze and solve the problems of wave propagation in any nonhomogeneous unbounded domain. The proposed method has the ability to use the domain properties by coordinate as an input. Therefore, there is no restriction in the form of the domain properties, such as being periodical as in the case of existing similar numerical methods. The proposed method can model the boundary points between phases with trace of errors and the results of this method satisfy both conditions of decay and radiation.

  18. The Potential for Wave Energy in the North Sea

    DEFF Research Database (Denmark)

    Sørensen, H. C.; Chozas, Julia Fernandez

    2010-01-01

    the North Sea are expected to change the priority in favour of utilising wave energy from the North Sea. The paper describes the opportunities for power production in the North Sea considering the competition for space and the synergy with offshore wind. Two approaches are used: a traditional national......The North Sea has not yet been regarded as prime area for wave energy development in Europe except in Denmark, Benelux and Germany. The reason is the relatively low intensity of waves (12-17kW/m) compared to the Atlantic with a wave climate of 24-48kW/m. Further on the design wave load is almost...... as in the Atlantic and the distance to shore relatively long compared to sites with good wave climate like Ireland, Portugal, Spain and the west coast of UK. The increasing activities within offshore wind in the North Sea and the attempt to build a super grid connecting the wind sites with the major consumers around...

  19. RANS Simulation of the Heave Response of a Two-Body Floating Point Wave Absorber: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Y.; Li, Y.

    2011-03-01

    A preliminary study on a two-body floating wave absorbers is presented in this paper. A Reynolds-Averaged Navier-Stokes computational method is applied for analyzing the hydrodynamic heave response of the absorber in operational wave conditions. The two-body floating wave absorber contains a float section and a submerged reaction section. For validation purposes, our model is first assumed to be locked. The two sections are forced to move together with each other. The locked single body model is used in a heave decay test, where the RANS result is validated with the experimental measurement. For the two-body floating point absorber simulation, the two sections are connected through a mass-spring-damper system, which is applied to simulate the power take-off mechanism under design wave conditions. Overall, the details of the flow around the absorber and its nonlinear interaction with waves are investigated, and the power absorption efficiency of the two-body floating wave absorber in waves with a constant value spring-damper system is examined.

  20. System for harvesting water wave energy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhong Lin; Su, Yanjie; Zhu, Guang; Chen, Jun

    2016-07-19

    A generator for harvesting energy from water in motion includes a sheet of a hydrophobic material, having a first side and an opposite second side, that is triboelectrically more negative than water. A first electrode sheet is disposed on the second side of the sheet of a hydrophobic material. A second electrode sheet is disposed on the second side of the sheet of a hydrophobic material and is spaced apart from the first electrode sheet. Movement of the water across the first side induces an electrical potential imbalance between the first electrode sheet and the second electrode sheet.

  1. Beam energy dependence of Hanbury-Brown-Twiss radii from a blast-wave model

    CERN Document Server

    Zhang, S; Chen, J H; Zhong, C

    2016-01-01

    Beam energy dependence of correlation lengths (Hanbury-Brown-Twiss radii) is calculated by using a blast-wave model and the results are comparable with those from RHIC-STAR beam energy scan data as well as the LHC-ALICE measurements. The parameters for the blast-wave model as a function of beam energy are configured by fitting Hanbury-Brown-Twiss radii at each energy point. Transverse momentum dependence of Hanbury-Brown-Twiss radii are presented with the extracted parameters for $\\sqrt{s_{NN}} = $ 200 GeV and 2.76 TeV. From the results it can be found that particle emission duration can not be ignored while calculating Hanbury-Brown-Twiss radii with the same parameters. And tuning kinetic freeze-out temperature in a range will result in system lifetime changing in reverse direction as that in RHIC-STAR measurements.

  2. Comparative Study of Turbines for Wave Energy Conversion

    Institute of Scientific and Technical Information of China (English)

    Hideaki Maeda; Toshiaki Setoguchi; Manabu Takao; Keita Sakurada; Tae-Ho Kin; Kenji Kaneko

    2001-01-01

    The objective of this paper is to compare the performances of the turbines, which could be used for wave energy conversion in the near future, under various irregular wave conditions. The turbines included in the paper are as follows: (a) Wells turbine with guide vanes; (b) impulse turbine with self-pitch-controlled guide vanes; (c) impulse turbine with fixed guide vanes. In this study, experimental investigations were carried out to clarify the performances of the turbines under steady flow conditions, and then a numerical simulation was used for predicting the performances under irregular wave conditions with various significant wave heights. As a result, it was found that the running and starting characteristics of the impulse turbines could be superior to those of the Wells turbine.

  3. Point-by-point near-field optical energy deposition around plasmonic nanospheres in absorbing media.

    Science.gov (United States)

    Harrison, R K; Ben-Yakar, Adela

    2015-08-01

    Here we investigate the effects of absorbing media on plasmon-enhanced near-field optical energy deposition. We find that increasing absorption by the medium results in increased particle scattering at the expense of particle absorption, and that much of this increased particle scattering is absorbed by the medium close to the particle surface. We present an analytical method for evaluating the spatial distribution of near-field enhanced absorption surrounding plasmonic metal nanospheres in absorbing media using a new point-by-point method. We propose criteria to define relevant near-field boundaries and calculate the properties of the local absorption enhancement, which redistributes absorption to the near-field and decays asymptotically as a function of the distance from the particle to background levels. Using this method, we performed a large-scale parametric study to understand the effect of particle size and wavelength on the near-field absorption for gold nanoparticles in aqueous media and silicon, and identified conditions that are relevant to enhanced local infrared absorption in silicon. The presented approach provides insight into the local energy transfer around plasmonic nanoparticles for predicting near-field effects for advanced concepts in optical sensing, thin-film solar cells, nonlinear imaging, and photochemical applications.

  4. Neural rotational speed control for wave energy converters

    Science.gov (United States)

    Amundarain, M.; Alberdi, M.; Garrido, A. J.; Garrido, I.

    2011-02-01

    Among the benefits arising from an increasing use of renewable energy are: enhanced security of energy supply, stimulation of economic growth, job creation and protection of the environment. In this context, this study analyses the performance of an oscillating water column device for wave energy conversion in function of the stalling behaviour in Wells turbines, one of the most widely used turbines in wave energy plants. For this purpose, a model of neural rotational speed control system is presented, simulated and implemented. This scheme is employed to appropriately adapt the speed of the doubly-fed induction generator coupled to the turbine according to the pressure drop entry, so as to avoid the undesired stalling behaviour. It is demonstrated that the proposed neural rotational speed control design adequately matches the desired relationship between the slip of the doubly-fed induction generator and the pressure drop input, improving the power generated by the turbine generator module.

  5. Vertical Distribution of Wave Overtopping for Design of Multi Level Overtopping Based Wave Energy Converters

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter

    2007-01-01

    This paper presents an expression describing the vertical distribution of overtopping, the experimental work leading to this, as well as the use of the expression for numerical optimization of the geometrical layout of the multi level overtopping based wave energy converter Seawave Slot-cone Gene......This paper presents an expression describing the vertical distribution of overtopping, the experimental work leading to this, as well as the use of the expression for numerical optimization of the geometrical layout of the multi level overtopping based wave energy converter Seawave Slot...

  6. Wave loadings acting on Overtopping Breakwater for Energy Conversion

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Nørgaard, Jørgen Harck; Contestabile, Pasquale

    2013-01-01

    distributions. Load measurements were compared with the most used prediction method for traditional breakwaters, available in the Coastal Engineering Manual (U.S. Army Corps of Engineers, 2002). These results suggest to use the experimental data as design loadings since the design criteria for the innovative......Any kind of Wave Energy Converter (WEC) requires information on reliability of technology and on time required for the return of the investment (reasonable payback). The structural response is one of the most important parameters to take in to account for a consistent assessment on innovative...... devices. This paper presents results on wave loading acting on an hybrid WEC named Overtopping BReakwater for Energy Conversion (OBREC). The new design is based on the concept of an integration between a traditional rubble mound breakwater and a front reservoir designed to store the wave overtopping from...

  7. Energy Content & Spectral Energy Representation of Wave Propagation in a Granular Chain

    Science.gov (United States)

    Shrivastava, Rohit; Luding, Stefan

    2017-04-01

    A mechanical wave is propagation of vibration with transfer of energy and momentum. Studying the energy as well as spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through materials like soil. The study of these properties is aimed at modeling wave propagation for oil, mineral or gas exploration (seismic prospecting) or non-destructive testing for the study of internal structure of solids. Wave propagation through granular materials is often accompanied by energy attenuation which is quantified by Quality factor and this parameter has often been used to characterize material properties, hence, determining the Quality factor (energy attenuation parameter) can also help in determining the properties of the material [3], studied experimentally in [2]. The study of Energy content (Kinetic, Potential and Total Energy) of a pulse propagating through an idealized one-dimensional discrete particle system like a mass disordered granular chain can assist in understanding the energy attenuation due to disorder as a function of propagation distance. The spectral analysis of the energy signal can assist in understanding dispersion as well as attenuation due to scattering in different frequencies (scattering attenuation). The selection of one-dimensional granular chain also helps in studying only the P-wave attributes of the wave and removing the influence of shear or rotational waves. Granular chains with different mass distributions have been studied, by randomly selecting masses from normal, binary and uniform distributions and the standard deviation of the distribution is considered as the disorder parameter, higher standard deviation means higher disorder and lower standard deviation means lower disorder [1]. For obtaining macroscopic/continuum properties, ensemble averaging has been invoked. Instead of analyzing deformation-, velocity- or stress

  8. Conversion of the zero-point energy of the quantum vacuum into classical mechanical energy

    Energy Technology Data Exchange (ETDEWEB)

    Turtur, Claus Wilhelm

    2010-07-01

    A perpetual motion machine - this can never exist. But energy sources nearly disregarded up to now - they exist. These are energy sources, which have been hardly under investigation, so that mankind did not yet learn how to get benefit from them. Most part of the universe consists of such energy, which is still called 'invisible'. A part of this energy is to be found within the so called zero-point oscillations of the quantum vacuum, thus within the empty void from the perspective of quantum physics. The author of the book is physicist. He theoretically developed and then experimentally verified a method for the conversion of vacuum energy into classical mechanical energy. His technique is one of the very few approaches known up to know. The most prominent approaches to convert vacuum energy are described in this book in many scientific details, and they are compared with other known proposals for the use of vacuum energy. (orig.)

  9. Design Specifications for the Hanstholm WEPTOS Wave Energy Converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter; Larsen, Tommy

    2012-01-01

    -moored and floating structure absorbs the energy of the waves through a multitude of rotors. The shape of the rotors is based on the renowned Salter’s Duck. On each leg, the rotors pivot around a common axle, through which the rotors transfer the absorbed power to a common power take off system. The study...

  10. Experimental Study on a Rotor for WEPTOS Wave Energy Converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter; Marchalot, Tanguy

    This report presents the results of an experimental study of the power conversion capabilities of one single rotor of the WEPTOS wave energy converter. The investigation focuses mainly on defining the optimal weight distribution in the rotor in order to improve the hydraulic performance through...

  11. Hydraulic Evaluation of the LEANCON Wave Energy Converter

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Frigaard, Peter

    This report is a product of the co-operation agreement between Aalborg University and LEANCON (by Kurt Due Rasmussen) on the evaluation and development of the LEANCON wave energy converter (WEC). The work reported here has focused on evaluation of the power production of the device, based...

  12. Experimental testing of moorings for large floating wave energy converters

    DEFF Research Database (Denmark)

    Thomsen, Jonas Bjerg; Ferri, Francesco; Kofoed, Jens Peter

    2016-01-01

    This paper presents the outcome of a test campaign, which investigates the behaviour of a synthetic mooring system applied to the Floating Power Plant wave energy converter. The study investigates the motion and tension response under operational and extreme sea states expected at the deployment...

  13. Recent Developments of Wave Energy Utilization in Denmark

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Frigaard, Peter; Kramer, Morten

    2006-01-01

    This paper aims at giving an overview of the developments researchers at the Department of Civil Engineering, Aalborg University, Denmark (DCE), have been involved in within the field of wave energy utilization in Denmark over the past decade. At first a general introduction is given followed by ...

  14. Effect of spatial discretization of energy on detonation wave propagation

    CERN Document Server

    Mi, XiaoCheng; Higgins, Andrew J

    2016-01-01

    Detonation propagation in the limit of highly spatially discretized energy sources is investigated. The model of this problem begins with a medium consisting of a calorically perfect gas with a prescribed energy release per unit mass. The energy release is collected into sheet-like sources that are now embedded in an inert gas that fills the spaces between them. The release of energy in the first sheet results in a planar blast wave that propagates to the next source, which is triggered after a prescribed delay, generating a new blast, and so forth. The resulting wave dynamics as the front passes through hundreds of such sources is computationally simulated by numerically solving the governing one-dimensional Euler equations in the lab-fixed reference frame. The average wave speed for each simulation is measured once the wave propagation has reached a quasi-periodic solution. Velocities in excess of the CJ speed are found as the sources are made increasingly discrete, with the deviation above CJ being as grea...

  15. Optimization of Overtopping Wave Energy Converters by Geometry Control

    DEFF Research Database (Denmark)

    Victor, L.; Troch, P.; Kofoed, Jens Peter

    2011-01-01

    In this paper, the results of a study on the effects of geometry control on the performance of overtopping wave energy converters with a simple geometry built in coastal structures (simple OWECs) are presented. Empirical formulae, derived based on experimental tests on simple OWECs with varying...

  16. Aiding Design of Wave Energy Converters via Computational Simulations

    Science.gov (United States)

    Jebeli Aqdam, Hejar; Ahmadi, Babak; Raessi, Mehdi; Tootkaboni, Mazdak

    2015-11-01

    With the increasing interest in renewable energy sources, wave energy converters will continue to gain attention as a viable alternative to current electricity production methods. It is therefore crucial to develop computational tools for the design and analysis of wave energy converters. A successful design requires balance between the design performance and cost. Here an analytical solution is used for the approximate analysis of interactions between a flap-type wave energy converter (WEC) and waves. The method is verified using other flow solvers and experimental test cases. Then the model is used in conjunction with a powerful heuristic optimization engine, Charged System Search (CSS) to explore the WEC design space. CSS is inspired by charged particles behavior. It searches the design space by considering candidate answers as charged particles and moving them based on the Coulomb's laws of electrostatics and Newton's laws of motion to find the global optimum. Finally the impacts of changes in different design parameters on the power takeout of the superior WEC designs are investigated. National Science Foundation, CBET-1236462.

  17. Experimental testing of moorings for large floating wave energy converters

    DEFF Research Database (Denmark)

    Thomsen, Jonas Bjerg; Ferri, Francesco; Kofoed, Jens Peter

    2016-01-01

    This paper presents the outcome of a test campaign, which investigates the behaviour of a synthetic mooring system applied to the Floating Power Plant wave energy converter. The study investigates the motion and tension response under operational and extreme sea states expected at the deployment ...

  18. Design of a magnetic lead screw for wave energy conversion

    DEFF Research Database (Denmark)

    Holm, Rasmus Koldborg; Berg, Nick Ilsoe; Walkusch, Morten

    2013-01-01

    This paper deals with the development of a magnetic lead screw (MLS) for wave energy conversion. Initially, a brief state of the art regarding linear permanent-magnet generators and MLSs is given, leading to an introduction of the MLS and a presentation of the results from a finite-element analysis...

  19. Design of a magnetic lead screw for wave energy conversion

    DEFF Research Database (Denmark)

    Holm, Rasmus Koldborg; Berg, Nick Ilsø; Rasmussen, Peter Omand

    2012-01-01

    This paper deals with the development of a magnetic lead screw (MLS) for wave energy conversion. Initially, a brief state-of-the-art regarding linear PM generators and magnetic lead screws is given, leading to an introduction of the magnetic lead screw and a presentation of the results from...

  20. Structural Optimization of Triboelectric Nanogenerator for Harvesting Water Wave Energy.

    Science.gov (United States)

    Jiang, Tao; Zhang, Li Min; Chen, Xiangyu; Han, Chang Bao; Tang, Wei; Zhang, Chi; Xu, Liang; Wang, Zhong Lin

    2015-12-22

    Ocean waves are one of the most abundant energy sources on earth, but harvesting such energy is rather challenging due to various limitations of current technologies. Recently, networks formed by triboelectric nanogenerator (TENG) have been proposed as a promising technology for harvesting water wave energy. In this work, a basic unit for the TENG network was studied and optimized, which has a box structure composed of walls made of TENG composed of a wavy-structured Cu-Kapton-Cu film and two FEP thin films, with a metal ball enclosed inside. By combination of the theoretical calculations and experimental studies, the output performances of the TENG unit were investigated for various structural parameters, such as the size, mass, or number of the metal balls. From the viewpoint of theory, the output characteristics of TENG during its collision with the ball were numerically calculated by the finite element method and interpolation method, and there exists an optimum ball size or mass to reach maximized output power and electric energy. Moreover, the theoretical results were well verified by the experimental tests. The present work could provide guidance for structural optimization of wavy-structured TENGs for effectively harvesting water wave energy toward the dream of large-scale blue energy.

  1. Experimental Modelling of the Overtopping Flow on the Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Kofoed, Jens Peter

    The Wave Dragon is a floating slack-moored Wave Energy Converter (WEC) of the overtopping type. Oncoming waves are focused by two wing reflectors towards the ramp of the device, surge-up and overtop into a reservoir placed at a higher level than the surface of the sea. The energy production takes...... place as the water is led back to the sea through a set of low-head hydro-turbines. After many years of development, Wave Dragon (WD) is now facing the phase of pre-commercial demonstration. In this phase it is very important to be able to use the available data to predict the performances of the device...... form) is transferred to the device in the form of volumes of water coming into the reservoir. These volumes are stored at a higher level than the surrounding sea, being a stock of potential energy. 2. Secondary energy conversion: turbines – The potential energy stored in the reservoir is transformed...

  2. Power Take-Off Simulation for Scale Model Testing of Wave Energy Converters

    Directory of Open Access Journals (Sweden)

    Scott Beatty

    2017-07-01

    Full Text Available Small scale testing in controlled environments is a key stage in the development of potential wave energy conversion technology. Furthermore, it is well known that the physical design and operational quality of the power-take off (PTO used on the small scale model can have vast effects on the tank testing results. Passive mechanical elements such as friction brakes and air dampers or oil filled dashpots are fraught with nonlinear behaviors such as static friction, temperature dependency, and backlash, the effects of which propagate into the wave energy converter (WEC power production data, causing very high uncertainty in the extrapolation of the tank test results to the meaningful full ocean scale. The lack of quality in PTO simulators is an identified barrier to the development of WECs worldwide. A solution to this problem is to use actively controlled actuators for PTO simulation on small scale model wave energy converters. This can be done using force (or torque-controlled feedback systems with suitable instrumentation, enabling the PTO to exert any desired time and/or state dependent reaction force. In this paper, two working experimental PTO simulators on two different wave energy converters are described. The first implementation is on a 1:25 scale self-reacting point absorber wave energy converter with optimum reactive control. The real-time control system, described in detail, is implemented in LabVIEW. The second implementation is on a 1:20 scale single body point absorber under model-predictive control, implemented with a real-time controller in MATLAB/Simulink. Details on the physical hardware, software, and feedback control methods, as well as results, are described for each PTO. Lastly, both sets of real-time control code are to be web-hosted, free for download, modified and used by other researchers and WEC developers.

  3. Wave Energy Converter (WEC) Array Effects on Wave Current and Sediment Circulation: Monterey Bay CA.

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Jesse D.; Jones, Craig; Magalen, Jason

    2014-09-01

    The goal s of this study were to develop tools to quantitatively characterize environments where wave energy converter ( WEC ) devices may be installed and to assess e ffects on hydrodynamics and lo cal sediment transport. A large hypothetical WEC array was investigated using wave, hydrodynamic, and sediment transport models and site - specific average and storm conditions as input. The results indicated that there were significant changes in sediment s izes adjacent to and in the lee of the WEC array due to reduced wave energy. The circulation in the lee of the array was also altered; more intense onshore currents were generated in the lee of the WECs . In general, the storm case and the average case show ed the same qualitative patterns suggesting that these trends would be maintained throughout the year. The framework developed here can be used to design more efficient arrays while minimizing impacts on nearshore environmen ts.

  4. R&D Towards Commercialization of Sea Wave Slot Cone Generator (SSG) Overtopping Wave Energy Converter

    DEFF Research Database (Denmark)

    Margheritini, Lucia

    a fruitful decade. Improvement of technologies together with financial support at different levels gave space to new ideas, bringing the research to gamble on different concepts. While innumerable projects went through an initial testing phase that lasts 5-10 years, only few of them reached the sea prototype...... between ventures and private investors, and to promote an accelerated shift from a technology to a market focus. This Thesis is presented as a collection of works published by the author on her research on the Sea wave Slot cone Generator wave energy converter. These include 1 accepted and 2 submitted...... journal papers; 7 peer-reviewed conference papers. The results are based on laboratory tests, numerical simulations and feasibility studies. Research presented in this Thesis contributes to reduce the technical and non-technical risks associated to the wave energy sector and promotes accelerated shift...

  5. Stochastic control of inertial sea wave energy converter.

    Science.gov (United States)

    Raffero, Mattia; Martini, Michele; Passione, Biagio; Mattiazzo, Giuliana; Giorcelli, Ermanno; Bracco, Giovanni

    2015-01-01

    The ISWEC (inertial sea wave energy converter) is presented, its control problems are stated, and an optimal control strategy is introduced. As the aim of the device is energy conversion, the mean absorbed power by ISWEC is calculated for a plane 2D irregular sea state. The response of the WEC (wave energy converter) is driven by the sea-surface elevation, which is modeled by a stationary and homogeneous zero mean Gaussian stochastic process. System equations are linearized thus simplifying the numerical model of the device. The resulting response is obtained as the output of the coupled mechanic-hydrodynamic model of the device. A stochastic suboptimal controller, derived from optimal control theory, is defined and applied to ISWEC. Results of this approach have been compared with the ones obtained with a linear spring-damper controller, highlighting the capability to obtain a higher value of mean extracted power despite higher power peaks.

  6. WEC3: Wave Energy Converter Code Comparison Project: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Combourieu, Adrien; Lawson, Michael; Babarit, Aurelien; Ruehl, Kelley; Roy, Andre; Costello, Ronan; Laporte Weywada, Pauline; Bailey, Helen

    2017-01-01

    This paper describes the recently launched Wave Energy Converter Code Comparison (WEC3) project and present preliminary results from this effort. The objectives of WEC3 are to verify and validate numerical modelling tools that have been developed specifically to simulate wave energy conversion devices and to inform the upcoming IEA OES Annex VI Ocean Energy Modelling Verification and Validation project. WEC3 is divided into two phases. Phase 1 consists of a code-to-code verification and Phase II entails code-to-experiment validation. WEC3 focuses on mid-fidelity codes that simulate WECs using time-domain multibody dynamics methods to model device motions and hydrodynamic coefficients to model hydrodynamic forces. Consequently, high-fidelity numerical modelling tools, such as Navier-Stokes computational fluid dynamics simulation, and simple frequency domain modelling tools were not included in the WEC3 project.

  7. 75 FR 16201 - FPL Energy Point Beach, LLC; Point Beach Nuclear Plant, Units 1 and 2; Exemption

    Science.gov (United States)

    2010-03-31

    ... From the Federal Register Online via the Government Publishing Office ] NUCLEAR REGULATORY COMMISSION FPL Energy Point Beach, LLC; Point Beach Nuclear Plant, Units 1 and 2; Exemption 1.0 Background... letter from R. W. Borchardt (NRC) to M. S. Fertel (Nuclear Energy Institute) dated June 4, 2009. The...

  8. Wave loadings acting on innovative rubble mound breakwater for overtopping wave energy conversion

    DEFF Research Database (Denmark)

    Contestabile, Pasquale; Iuppa, Claudio; Lauro, Enrico Di

    2017-01-01

    Highlights •An innovative breakwater for overtopping wave energy conversion has been studied. •Physical model tests have been carried out and analysed. •Breakwater design information on loadings acting on various parts of the structure has been presented. •Design formulae and validation of some...

  9. Preliminary Results from Second Phase Sea Testing of the Wave Dragon Prototype Wave Energy Converter

    DEFF Research Database (Denmark)

    Soerensen, Hans Chr.; Tedd, James; Friis-Madsen, Erik;

    2006-01-01

    In March 2006 the prototype Wave Dragon has been redeployed to a more energetic site in Nissum Bredning an inland sea in Western Denmark. This has followed a period of renovation of many aspects of the device which have resulted in 20% higher energy output. This paper describes the preliminary re...

  10. Preliminary Results from Second Phase Sea Testing of the Wave Dragon Prototype Wave Energy Converter

    DEFF Research Database (Denmark)

    Soerensen, Hans Chr.; Tedd, James; Friis-Madsen, Erik

    2006-01-01

    In March 2006 the prototype Wave Dragon has been redeployed to a more energetic site in Nissum Bredning an inland sea in Western Denmark. This has followed a period of renovation of many aspects of the device which have resulted in 20% higher energy output. This paper describes the preliminary...

  11. Uncertainty in wave energy resource assessment. Part 1: Historic data

    Energy Technology Data Exchange (ETDEWEB)

    Mackay, Edward B.L.; Bahaj, AbuBakr S. [Sustainable Energy Research Group, School of Civil Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Challenor, Peter G. [Ocean Observing and Climate Group, National Oceanography Centre, Southampton SO14 3ZH (United Kingdom)

    2010-08-15

    The uncertainty in estimates of the energy yield from a wave energy converter (WEC) is considered. The study is presented in two articles. This first article deals with the accuracy of the historic data and the second article considers the uncertainty which arises from variability in the wave climate. Estimates of the historic resource for a specific site are usually calculated from wave model data calibrated against in-situ measurements. Both the calibration of model data and estimation of confidence bounds are made difficult by the complex structure of errors in model data. Errors in parameters from wave models exhibit non-linear dependence on multiple factors, seasonal and interannual changes in bias and short-term temporal correlation. An example is given using two hindcasts for the European Marine Energy Centre in Orkney. Before calibration, estimates of the long-term mean WEC power from the two hindcasts differ by around 20%. The difference is reduced to 5% after calibration. The short-term temporal evolution of errors in WEC power is represented using ARMA models. It is shown that this is sufficient to model the long-term uncertainty in estimated WEC yield from one hindcast. However, seasonal and interannual changes in model biases in the other hindcast cause the uncertainty in estimated long-term WEC yield to exceed that predicted by the ARMA model. (author)

  12. Wave energy absorption by a floating air bag

    DEFF Research Database (Denmark)

    Kurniawan, Adi; Chaplin, John; Greaves, Deborah

    2017-01-01

    A floating air bag, ballasted in water, expands and contracts as it heaves under wave action. Connecting the bag to a secondary volume via a turbine transforms the bag into a device capable of generating useful energy from the waves. Small-scale measurements of the device reveal some interesting...... properties, which are successfully predicted numerically. Owing to its compressibility, the device can have a heave resonance period longer than that of a rigid device of the same shape and size, without any phase control. Furthermore, varying the amount of air in the bag is found to change its shape...

  13. Floating attenuator wave energy device. Wavegen HYDRA project

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    The Wavegen Project which set out to develop a floating externally tensioned articulated wave-energy generator based on work carried out at RMCS Shrivenham in the 1980s has been abandoned until further notice. The computer modelling carried out in the early days indicated much promise, but the promise turned to disappointment when difficulties cropped-up in attempting to put the design into practice. A particular problem arose in matching the external tension to an equivalent beam stiffness to tune the natural bending frequency of the raft to that of the driving waves. A further eleven practical problems encountered are discussed.

  14. Modeling and Simulation of a Wave Energy Converter INWAVE

    Directory of Open Access Journals (Sweden)

    Seung Kwan Song

    2017-01-01

    Full Text Available INGINE Inc. developed its own wave energy converter (WEC named INWAVE and has currently installed three prototype modules in Jeju Island, Korea. This device is an on-shore-type WEC that consists of a buoy, pulleys fixed to the sea-floor and a power take off module (PTO. Three ropes are moored tightly on the bottom of the buoy and connected to the PTO via the pulleys, which are moving back and forth according to the motion of the buoy. Since the device can harness wave energy from all six degrees of movement of the buoy, it is possible to extract energy efficiently even under low energy density conditions provided in the coastal areas. In the PTO module, the ratchet gears convert the reciprocating movement of the rope drum into a uni-directional rotation and determine the transmission of power from the relation of the angular velocities between the rope drum and the generator. In this process, the discontinuity of the power transmission occurs and causes the modeling divergence. Therefore, we introduce the concept of the virtual torsion spring in order to prevent the impact error in the ratchet gear module, thereby completing the PTO modeling. In this paper, we deal with dynamic analysis in the time domain, based on Newtonian mechanics and linear wave theory. We derive the combined dynamics of the buoy and PTO modules via geometric relation between the buoy and mooring ropes, then suggest the ratchet gear mechanism with the virtual torsion spring element to reduce the dynamic errors during the phase transitions. Time domain simulation is carried out under irregular waves that reflect the actual wave states of the installation area, and we evaluate the theoretical performance using the capture width ratio.

  15. Zero-point energy effects in anion solvation shells.

    Science.gov (United States)

    Habershon, Scott

    2014-05-21

    By comparing classical and quantum-mechanical (path-integral-based) molecular simulations of solvated halide anions X(-) [X = F, Cl, Br and I], we identify an ion-specific quantum contribution to anion-water hydrogen-bond dynamics; this effect has not been identified in previous simulation studies. For anions such as fluoride, which strongly bind water molecules in the first solvation shell, quantum simulations exhibit hydrogen-bond dynamics nearly 40% faster than the corresponding classical results, whereas those anions which form a weakly bound solvation shell, such as iodide, exhibit a quantum effect of around 10%. This observation can be rationalized by considering the different zero-point energy (ZPE) of the water vibrational modes in the first solvation shell; for strongly binding anions, the ZPE of bound water molecules is larger, giving rise to faster dynamics in quantum simulations. These results are consistent with experimental investigations of anion-bound water vibrational and reorientational motion.

  16. Energy policies avoiding a tipping point in the climate system

    Energy Technology Data Exchange (ETDEWEB)

    Bahn, Olivier [GERAD and Department of Management Sciences, HEC Montreal, Montreal (Qc) (Canada); Edwards, Neil R. [Earth and Environmental Sciences, CEPSAR, Open University, Milton Keynes MK7 6AA (United Kingdom); Knutti, Reto [Institute for Atmospheric and Climate Science, ETH Zurich, CH-8092 Zurich (Switzerland); Stocker, Thomas F. [Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, CH-3012 Bern (Switzerland)

    2011-01-15

    Paleoclimate evidence and climate models indicate that certain elements of the climate system may exhibit thresholds, with small changes in greenhouse gas emissions resulting in non-linear and potentially irreversible regime shifts with serious consequences for socio-economic systems. Such thresholds or tipping points in the climate system are likely to depend on both the magnitude and rate of change of surface warming. The collapse of the Atlantic thermohaline circulation (THC) is one example of such a threshold. To evaluate mitigation policies that curb greenhouse gas emissions to levels that prevent such a climate threshold being reached, we use the MERGE model of Manne, Mendelsohn and Richels. Depending on assumptions on climate sensitivity and technological progress, our analysis shows that preserving the THC may require a fast and strong greenhouse gas emission reduction from today's level, with transition to nuclear and/or renewable energy, possibly combined with the use of carbon capture and sequestration systems. (author)

  17. Low-pressure hydro turbines and control equipment for wave energy converters (Wave Dragon). Final report

    Energy Technology Data Exchange (ETDEWEB)

    Soerensen, H.C.; Hansen, R.

    2001-06-01

    The Wave Dragon is a 4 MW floating offshore wave energy converter of the overtopping type. Through performing tests on a scale 1:50 model of the Wave Dragon, real-time overtopping time series were provided. These allowed the development of a feasible turbine and regulation strategy for handling the varying heads and flows occurring in the reservoir. A model turbine with a runner diameter of 340 mm was designed, and tested in a conventional turbine test stand. The results revealed very high efficiencies (91.3% peak efficiency), and more importantly a very flat performance curve yielding high turbine efficiency for the complete range of heads available at the Wave Dragon. A suitable power take-off and grid connection system was developed, addressing power quality issues, as well as more practical issues of flexible cabling solutions. It was concluded that feasible solutions to the technical barriers envisioned prior to the project had been found. Also means for improving the overtopping characteristics of the device were put forward. The feasibility of the Wave Dragon at original 1st generation design was investigated and key performance figures were given as net annual power production of 5.1-3.1 GWh/year, 2,775-3,150 Euro/kW in construction costs and a power production price of 0.19-0.27 Euro/kWh. The figures includes availability losses, all losses in the power train, and losses from restricted freedom of movement for two of the scenarios, with a wave energy potential of 16 and 24 kW/m wave front respectively. Significant scope for improvement, especially from enhanced overtopping from improved design, mass production and learning effects were also identified. Through implementing the known technical improvements to the Wave Dragon design identified through the project an annual net power production of 8.9 GWh/year and a production price of 0.12 Euro/kWh is foreseen for a 24 kW/m wave potential. With additional technical improvements, mass production benefits and

  18. Optimal Constant DC Link Voltage Operation of aWave Energy Converter

    Directory of Open Access Journals (Sweden)

    Mats Leijon

    2013-04-01

    Full Text Available This article proposes a simple and reliable damping strategy for wave powerfarm operation of small-scale point-absorber converters. The strategy is based on passiverectification onto a constant DC-link, making it very suitable for grid integration of the farm.A complete model of the system has been developed in Matlab Simulink, and uses real sitedata as input. The optimal constant DC-voltage is evaluated as a function of the significantwave height and energy period of the waves. The total energy output of the WEC is derivedfor one year of experimental site data. The energy output is compared for two cases, onewhere the optimal DC-voltage is determined and held constant at half-hour basis throughoutthe year, and one where a selected value of the DC-voltage is kept constant throughout theyear regardless of sea state.

  19. Preliminary Verification and Validation of WEC-Sim, an Open-Source Wave Energy Converter Design Tool: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Ruehl, K.; Michelen, C.; Kanner, S.; Lawson, M.; Yu, Y. H.

    2014-03-01

    To promote and support the wave energy industry, a wave energy converter (WEC) design tool, WEC-Sim, is being developed by Sandia National Laboratories and the National Renewable Energy Laboratory. In this paper, the WEC-Sim code is used to model a point absorber WEC designed by the U.S. Department of Energy's reference model project. Preliminary verification was performed by comparing results of the WEC-Sim simulation through a code-to-code comparison, utilizing the commercial codes ANSYS-AQWA, WaveDyn, and OrcaFlex. A preliminary validation of the code was also performed by comparing WEC-Sim simulation results to experimental wave tank tests.

  20. Measurements of overtopping flow time series on the Wave Dragon, wave energy converter

    Energy Technology Data Exchange (ETDEWEB)

    Tedd, James; Peter Kofoed, Jens [Department of Civil Engineering, Aalborg University, Sohngaardhomsvej 57, Aalborg 9000 (Denmark)

    2009-03-15

    A study of overtopping flow series on the Wave Dragon prototype, a low crested device designed to maximise flow, in a real sea, is presented. This study aims to fill the gap in the literature on time series of flow overtopping low crested structures. By comparing to a simulated flow the characteristics of the overtopping flow are discussed and the simulation algorithm is tested. Measured data is shown from a storm build up in October 2006, from the Wave Dragon prototype situated in an inland sea in Northern Denmark. This wave energy converter extracts energy from the waves, by funnelling them to run-up a ramp and overtop into a reservoir. This water is stored at a higher level than the average sea surface, before being discharged through hydro turbines. The waves, device sea handling and overtopping flow are measured by pressure transducers ahead of, beneath and in the device. Comparisons of the distribution and correlation show that the measurements support the use of the algorithm for generating a simulated flow. (author)

  1. Analysis of Energy Overshoot of High Frequency Waves with Wavelet Transform

    Institute of Scientific and Technical Information of China (English)

    WEN Fan

    2000-01-01

    A study is made on the overshoot phenomena in wind-generated waves. The surface displace ments of time-growing waves are measured at four fetches in a wind wave channel. The evolution of high frequency waves is displayed with wavelet transform. The results are compared with Sutherland's. It is found that high frequency wave components experience much stronger energy overshoot in the evolution.The energy of high frequency waves decreases greatly after overshoot

  2. Power inversion design for ocean wave energy harvesting

    Science.gov (United States)

    Talebani, Anwar N.

    The needs for energy sources are increasing day by day because of several factors, such as oil depletion, and global climate change due to the higher level of CO2, so the exploration of various renewable energy sources is very promising area of study. The available ocean waves can be utilized as free source of energy as the water covers 70% of the earth surface. This thesis presents the ocean wave energy as a source of renewable energy. By addressing the problem of designing efficient power electronics system to deliver 5 KW from the induction generator to the grid with less possible losses and harmonics as possible and to control current fed to the grid to successfully harvest ocean wave energy. We design an AC-DC full bridge rectifier converter, and a DC-DC boost converter to harvest wave energy from AC to regulated DC. In order to increase the design efficiency, we need to increase the power factor from (0.5-0.6) to 1. This is accomplished by designing the boost converter with power factor correction in continues mode with RC circuit as an input to the boost converter power factor correction. This design results in a phase shift between the input current and voltage of the full bridge rectifier to generate a small reactive power. The reactive power is injected to the induction generator to maintain its functionality by generating a magnetic field in its stator. Next, we design a single-phase pulse width modulator full bridge voltage source DC-AC grid-tied mode inverter to harvest regulated DC wave energy to AC. The designed inverter is modulated by inner current loop, to control current injected to the grid with minimal filter component to maintain power quality at the grid. The simulation results show that our design successfully control the current level fed to the grid. It is noteworthy that the simulated efficiency is higher than the calculated one since we used an ideal switch in the simulated circuit.

  3. Indelible Rules of Josephson Coupling Energy and Zero-Point Energy in High-Tc Cuprates

    Institute of Scientific and Technical Information of China (English)

    LIU Fu-Sui; CHEN Wan-Fang

    2004-01-01

    This paper shows that the Josephson coupling energy and the zero-point energy have indelible rules on the superfluid density and the superconductivity in the high-Tc cuprates.This paper also shows that the values of Tc at underdoped and overdoped regions are determined by the damage conditions of the phase coherence in the classical and the quantum XY-models,respectively.

  4. Comparison of Foundation Systems for Wave Energy Converters Wavestar

    DEFF Research Database (Denmark)

    Vaitkunaite, Evelina; Ibsen, Lars Bo; Nielsen, Benjaminn Nordahl;

    2013-01-01

    In order to deliver cost competitive solutions, Wave Energy Converters (WEC) must be optimized in several fields, e.g. transportation, installation, structure, machinery etc. Large expenses lie on the superstructure support, i.e. the offshore foundation. Geotechnical analysis and optimization....... In such a solution horizontal wind and wave loads are dominant. Gravity based, pile and bucket foundations are universally applied solutions for the offshore structures. The suitability of these types for a WEC is analysed and commented. The foundations are designed to satisfy ultimate and serviceability limit state...... of six possible foundation solutions for WEC are presented in this article. The study is performed for WEC superstructure supported by two or four foundations. In the four-column system horizontal wind and wave loads are transformed as a pair of vertical forces, acting in tension and compression. When...

  5. Wave energy fluxes and multi-decadal shoreline changes

    DEFF Research Database (Denmark)

    Kabuth, Alina Kristin; Kroon, Aart

    2014-01-01

    Spatial patterns of multidecadal shoreline changes in two microtidal, low-energetic embayments of southern Zealand, Denmark, were investigated by using the directional distribution of wave energy fluxes. The sites include a barrier island system attached to moraine bluffs, and a recurved spit...... adjacent to a cliff coast. The barrier island system is characterized by cross-shore translation and by an alignment of the barrier alongshore alternating directions of barrier-spit progradation in a bidirectional wave field. The recurved spit adjacent to the cliff coast experienced shoreline rotation...... through proximal erosion and distal lateral accretion in a unidirectional wave climate. The multidecadal shoreline changes were coupled to a slope-based morphological coastal classification. All erosive shores occurred within a narrow range of onshore and offshore coastal slopes. The alongshore...

  6. Identification of Swell in Nearshore Surface Wave Energy Spectra

    Directory of Open Access Journals (Sweden)

    Paul A. Work

    2010-06-01

    Full Text Available An approach for routine identification of swell and sea in nominally fully developed, omnidirectional, surface water wave energy spectra measured in arbitrary water depth is developed, applied, and discussed. The methodology is an extension of earlier work with deepwater spectra and involves identifying the frequency at which wave steepness is maximized and relating this to the swell separation frequency. The TMA parameterized spectrum is employed to establish a relationship between the two frequencies so that the methodology can be used when wind data are unavailable. The methodology is developed for finite water depth and tested using a dataset that includes both acoustic Doppler current profiler and wave buoy data, recorded simultaneously at the same location. For cases where the sea and swell are clearly, visually distinguishable in the omnidirectional spectra, the new method accurately distinguishes between the two, but it can also be used to identify sea and swell in unimodal spectra.

  7. A Thermodynamic Point of View on Dark Energy Models

    Directory of Open Access Journals (Sweden)

    Vincenzo F. Cardone

    2017-07-01

    Full Text Available We present a conjugate analysis of two different dark energy models, namely the Barboza–Alcaniz parameterization and the phenomenologically-motivated Hobbit model, investigating both their agreement with observational data and their thermodynamical properties. We successfully fit a wide dataset including the Hubble diagram of Type Ia Supernovae, the Hubble rate expansion parameter as measured from cosmic chronometers, the baryon acoustic oscillations (BAO standard ruler data and the Planck distance priors. This analysis allows us to constrain the model parameters, thus pointing at the region of the wide parameters space, which is worth focusing on. As a novel step, we exploit the strong connection between gravity and thermodynamics to further check models’ viability by investigating their thermodynamical quantities. In particular, we study whether the cosmological scenario fulfills the generalized second law of thermodynamics, and moreover, we contrast the two models, asking whether the evolution of the total entropy is in agreement with the expectation for a closed system. As a general result, we discuss whether thermodynamic constraints can be a valid complementary way to both constrain dark energy models and differentiate among rival scenarios.

  8. Low energy electron point source microscopy: beyond imaging.

    Science.gov (United States)

    Beyer, André; Gölzhäuser, Armin

    2010-09-01

    Low energy electron point source (LEEPS) microscopy has the capability to record in-line holograms at very high magnifications with a fairly simple set-up. After the holograms are numerically reconstructed, structural features with the size of about 2 nm can be resolved. The achievement of an even higher resolution has been predicted. However, a number of obstacles are known to impede the realization of this goal, for example the presence of electric fields around the imaged object, electrostatic charging or radiation induced processes. This topical review gives an overview of the achievements as well as the difficulties in the efforts to shift the resolution limit of LEEPS microscopy towards the atomic level. A special emphasis is laid on the high sensitivity of low energy electrons to electrical fields, which limits the structural determination of the imaged objects. On the other hand, the investigation of the electrical field around objects of known structure is very useful for other tasks and LEEPS microscopy can be extended beyond the task of imaging. The determination of the electrical resistance of individual nanowires can be achieved by a proper analysis of the corresponding LEEPS micrographs. This conductivity imaging may be a very useful application for LEEPS microscopes.

  9. Wave Energy Estimation by Using A Statistical Analysis and Wave Buoy Data near the Southern Caspian Sea

    Institute of Scientific and Technical Information of China (English)

    A.R.Zamani; M.A.Badri

    2015-01-01

    Statistical analysis was done on simultaneous wave and wind using data recorded by discus-shape wave buoy. The area is located in the southern Caspian Sea near the Anzali Port. Recorded wave data were obtained through directional spectrum wave analysis. Recorded wind direction and wind speed were obtained through the related time series as well. For 12-month measurements (May 25 2007-2008), statistical calculations were done to specify the value of nonlinear auto-correlation of wave and wind using the probability distribution function of wave characteristics and statistical analysis in various time periods. The paper also presents and analyzes the amount of wave energy for the area mentioned on the basis of available database. Analyses showed a suitable comparison between the amounts of wave energy in different seasons. As a result, the best period for the largest amount of wave energy was known. Results showed that in the research period, the mean wave and wind auto correlation were about three hours. Among the probability distribution functions, i.e Weibull, Normal, Lognormal and Rayleigh, “Weibull” had the best consistency with experimental distribution function shown in different diagrams for each season. Results also showed that the mean wave energy in the research period was about 49.88 kW/m and the maximum density of wave energy was found in February and March, 2010.

  10. Study of a Novel Oscillating Surge Wave Energy Converter: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Tom, Nathan M [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-08-01

    This study investigates the performance of an oscillating surge wave energy converter (OSWEC) that utilizes adjustable geometry as a means of controlling the hydrodynamic coefficients, a concept originally proposed by [1]. The body of the device consists of a bottom-hinged solid rectangular frame with five horizontal flaps spanning the interior of the frame. The flaps can rotate independently about their center of rotation within the frame like a large window shutter. Changing the orientation of the flaps alters the hydrodynamic coefficients and natural frequency of the device as well as the ability to shed or absorb structural loads accordingly. This ability may allow the device to operate in a wider range of sea states than other current wave energy converter designs. This paper presents and compares the results of numerical simulations and experimental testing of the OSWEC's response to regular waves with all five of the horizontal fin configurations sharing the same orientation of 0 degrees (fully closed interior) and 90 degrees (fully open). The numerical simulations were performed using WAMIT, which calculates hydrodynamic coefficients using a boundary element method code to solve the linear potential flow problem, and WEC-Sim, a MATLAB-based tool that simulates multibody devices in the time domain by solving the governing equations of motion. A 1:14 scale model of the device was built for experimental evaluation in an 8-m-long, 1-m wide wave tank, which supports a water depth of 0.7 m. The OSWEC motion in different wave conditions was measured with displacement sensors while nonlinear wave-structure interaction effects like slamming and overtopping were captured using a high-speed camera and used to understand differences between the simulation and experiments.

  11. Primordial blackholes and gravitational waves for an inflection-point model of inflation

    OpenAIRE

    Choudhury, Sayantan; Mazumdar, Anupam

    2014-01-01

    In this article we provide a new closed relationship between cosmic abundance of primordial gravitational waves and primordial blackholes that originated from initial inflationary perturbations for inflection-point models of inflation where inflation occurs below the Planck scale. The current Planck constraint on tensor-to-scalar ratio, running of the spectral tilt, and from the abundance of dark matter content in the universe, we can deduce a strict bound on the current abundance of primordi...

  12. Light propagation in local and linear media: Fresnel-Kummer wave surfaces with 16 singular points

    CERN Document Server

    Favaro, Alberto

    2016-01-01

    It is known that the Fresnel wave surfaces of transparent biaxial media have 4 singular points, located on two special directions. We show that, in more general media, the number of singularities can exceed 4. In fact, a highly symmetric linear material is proposed whose Fresnel surface exhibits 16 singular points. Because, for every linear material, the dispersion equation is quartic, we conclude that 16 is the maximum number of singularities. The identity of Fresnel and Kummer surfaces, which holds true for media with a certain symmetry (zero skewon piece), provides an elegant interpretation of the results. We describe a metamaterial realization for our linear medium with 16 singular points. It is found that an appropriate combination of metal bars, split-ring resonators, and magnetized particles can generate the correct permittivity, permeability, and magnetoelectric moduli. Lastly, we discuss the arrangement of the singularities in terms of Kummer's (16,6)-configuration of points and planes. An investigat...

  13. On the independent points in the sky for the search of periodic gravitational wave

    CERN Document Server

    Sahay, S K

    2008-01-01

    We investigate the independent points in the sky require to search the periodic gravitational wave, assuming the noise power spectral density to be flat. We have made an analysis with different initial azimuth of the Earth for a week data set. The analysis shows significant difference in the independent points in the sky for the search. We numerically obtain an approximate relation to make trade-off between computational cost and sensitivities. We also discuss the feasibility of the coherent search in small frequency band in reference to advanced LIGO.

  14. Characterization of wave physics in acoustic metamaterials using a fiber optic point detector

    Science.gov (United States)

    Ganye, Randy; Chen, Yongyao; Liu, Haijun; Bae, Hyungdae; Wen, Zhongshan; Yu, Miao

    2016-06-01

    Due to limitations of conventional acoustic probes, full spatial field mapping (both internal and external wave amplitude and phase measurements) in acoustic metamaterials with deep subwavelength structures has not yet been demonstrated. Therefore, many fundamental wave propagation phenomena in acoustic metamaterials remain experimentally unexplored. In this work, we realized a miniature fiber optic acoustic point detector that is capable of omnidirectional detection of complex spatial acoustic fields in various metamaterial structures over a broadband spectrum. By using this probe, we experimentally characterized the wave-structure interactions in an anisotropic metamaterial waveguide. We further demonstrated that the spatial mapping of both internal and external acoustic fields of metamaterial structures can help obtain important wave propagation properties associated with material dispersion and field confinement, and develop an in-depth understanding of the waveguiding physics in metamaterials. The insights and inspirations gained from our experimental studies are valuable not only for the advancement of fundamental metamaterial wave physics but also for the development of functional metamaterial devices such as acoustic lenses, waveguides, and sensors.

  15. Hydroelectromechanical modelling of a piezoelectric wave energy converter

    Science.gov (United States)

    Renzi, E.

    2016-11-01

    We investigate the hydroelectromechanical-coupled dynamics of a piezoelectric wave energy converter. The converter is made of a flexible bimorph plate, clamped at its ends and forced to motion by incident ocean surface waves. The piezoceramic layers are connected in series and transform the elastic motion of the plate into useful electricity by means of the piezoelectric effect. By using a distributed-parameter analytical approach, we couple the linear piezoelectric constitutive equations for the plate with the potential-flow equations for the surface water waves. The resulting system of governing partial differential equations yields a new hydroelectromechanical dispersion relation, whose complex roots are determined with a numerical approach. The effect of the piezoelectric coupling in the hydroelastic domain generates a system of short- and long-crested weakly damped progressive waves travelling along the plate. We show that the short-crested flexural wave component gives a dominant contribution to the generated power. We determine the hydroelectromechanical resonant periods of the device, at which the power output is significant.

  16. Direct Drive Wave Energy Buoy – 33rd scale experiment

    Energy Technology Data Exchange (ETDEWEB)

    Rhinefrank, Kenneth E. [Columbia Power Technologies, Inc.; Lenee-Bluhm, Pukha [Columbia Power Technologies, Inc.; Prudell, Joseph H. [Columbia Power Technologies, Inc.; Schacher, Alphonse A.; Hammagren, Erik J.; Zhang, Zhe [Columbia Power Technologies, Inc.

    2013-07-29

    Columbia Power Technologies (ColPwr) and Oregon State University (OSU) jointly conducted a series of tests in the Tsunami Wave Basin (TWB) at the O.H. Hinsdale Wave Research Laboratory (HWRL). These tests were run between November 2010 and February 2011. Models at 33rd scale representing Columbia Power’s Manta series Wave Energy Converter (WEC) were moored in configurations of one, three and five WEC arrays, with both regular waves and irregular seas generated. The primary research interest of ColPwr is the characterization of WEC response. The WEC response will be investigated with respect to power performance, range of motion and generator torque/speed statistics. The experimental results will be used to validate a numerical model. The primary research interests of OSU include an investigation into the effects of the WEC arrays on the near- and far-field wave propagation. This report focuses on the characterization of the response of a single WEC in isolation. To facilitate understanding of the commercial scale WEC, results will be presented as full scale equivalents.

  17. Efficiency of a gyroscopic device for conversion of mechanical wave energy to electrical energy

    DEFF Research Database (Denmark)

    Carlsen, Martin; Darula, Radoslav; Gravesen, Jens;

    2011-01-01

    We consider a recently proposed gyroscopic device for conversion of mechanical ocean wave energy to electrical energy. Two models of the device derived from standard engineering mechanics from the literature are analysed, and a model is derived from analytical mechanics considerations. From...

  18. Horizontal displacements contribution to tsunami wave energy balance

    CERN Document Server

    Dutykh, Denys; Chubarov, Leonid; Shokin, Yuriy

    2010-01-01

    The main reason for the generation of tsunamis is the deformation of the bottom of the ocean caused by an underwater earthquake. Usually, only the vertical bottom motion is taken into accound while the horizontal displacements are neglected. In the present paper we study both the vertical and the horizontal bottom motion while we propose a novel methodology for reconstructing the bottom coseismic displacements field which is transmitted to the free surface using a new three-dimensional Weakly Nonlinear (WN) approach. We pay a special attention to the evolution of kinetic and potential energies of the resulting wave while the contribution of horizontal displacements into wave energy balance is also quantified. Approaches proposed in this study are illustrated on the July 17, 2006 Java tsunami.

  19. Wave

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo

    2008-01-01

    Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many t...

  20. A New Methodology for Frequency Domain Analysis of Wave Energy Converters with Periodically Varying Physical Parameters

    Science.gov (United States)

    Mosher, Mark

    Within a wave energy converter's operational bandwidth, device operation tends to be optimal in converting mechanical energy into a more useful form at an incident wave period that is proximal to that of a power-producing mode of motion. Point absorbers, a particular classification of wave energy converters, tend to have a relative narrow optimal bandwidth. When not operating within the narrow optimal bandwidth, a point absorber's response and efficiency is attenuated. Given the wide range of sea-states that can be expected during a point absorber's operational life, these devices require a means to adjust, or control, their natural response to maximize the amount of energy absorbed in the large population of non-optimal conditions. In the field of wave energy research, there is considerable interest in the use of non-linear control techniques to this end. Non-linear control techniques introduce time-varying and state dependent control parameters into the point absorber motion equations, which usually motivates a computationally expensive numerical integration to determine the response of the device - important metrics such as gross converted power and relative travels of the device's pieces are extracted through post processing of the time series data. As an alternative, the work presented in this thesis was based on a closed form perturbation based approach for analysis of the response of a device with periodically-varying control parameters, subject to regular wave forcing, in the frequency domain. The proposed perturbation based method provides significant savings in computational time and enables the device's response to be represented in a closed form manner with a relatively small number of solution components - each component is comprised of a complex amplitude and oscillation frequency. This representation of the solution was found to be very concise and descriptive, and to lend itself to the calculation of gross absorbed power and travel constraint

  1. Efficient computation of GW energy level corrections for molecules described in a plane wave basis

    Science.gov (United States)

    Rousseau, Bruno; Laflamme Janssen, Jonathan; Côté, Michel

    2013-03-01

    An efficient computational approach is presented to compute the ionisation energy and quasiparticle band gap at the level of the GW approximation when the Hilbert space is described in terms of plane waves. The method relies on ab initio calculations as a starting point. Then, the use of the Sternheimer equation eliminates slowly convergent sums on conduction states. Further, the Lanczos method is used to efficiently extract the most important eigenstates of the dielectric operator. This approach avoids the explicit computation of matrix elements of the dielectric operator in the plane wave basis, a crippling bottleneck of the brute force approach. The method is initially applied to organic molecules of current interest in the field of organic photovoltaics. Given the completeness of the plane wave basis, systematic convergence studies can be conducted. Furthermore, the method can readily be extended to describe polymers, which are also of interest for photovoltaic applications, but remain a significant computational challenge for methods based on localized basis sets.

  2. High-Energy Waves in Superpolynomial FPU-Type Chains

    Science.gov (United States)

    Herrmann, Michael

    2017-02-01

    We consider periodic traveling waves in FPU-type chains with superpolynomial interaction forces and derive explicit asymptotic formulas for the high-energy limit as well as bounds for the corresponding approximation error. In the proof we adapt twoscale techniques that have recently been developed by Herrmann and Matthies for chains with singular potential and provide an asymptotic ODE for the scaled distance profile.

  3. Innovative Design for Sea Dikes and Breakwaters for Wave Energy Conversion

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Stagonas, Dimitris; Müller, Gerald

    2012-01-01

    This paper intends contributing to an economically and environmentally sustainable development of coastal infrastructures by investigating the possibility of combining together breakwaters and Wave Energy Converters (WEC). The latter change the wave energy to electricity, which may serve both the...

  4. Technical and Non-Technical Issues towards the Commercialisation of Wave Energy Converters

    DEFF Research Database (Denmark)

    Chozas, Julia Fernandez

    and the synergies in this area with offshore wind energy projects. . v. It studies the benefits of including wave energy in diversified renewable energy systems, chiefly with respect to power output variability and availability. . vi. It evaluates one of the most commonly claimed advantages for the wave energy...... sector: the predictability of waves, and assesses the value of wave forecasting in electricity markets. . vii. Lastly, it reviews the economic assessment of wave energy projects. . The scope of the thesis is broad and embraces subjects that can be categorised within technical and non......-technical disciplines. This combination of findings leads to an overview of the wave energy field and of WEC developments. It underlines hindrances that can affect developments when WECs are commissioned and the benefits wave energy brings to energy systems, especially when wave and wind generation is combined....

  5. Technical and Non-Technical Issues Towards the Commercialisation of Wave Energy Converters

    DEFF Research Database (Denmark)

    Chozas, Julia Fernandez

    it. iv. It investigates the opportunities to grid-connect offshore wave energy projects and the synergies in this area with offshore wind energy projects. v. It studies the benefits of including wave energy in diversified renewable energy systems, chiefly with respect to power output variability...... and availability. vi. It evaluates one of the most commonly claimed advantages for the wave energy sector: the predictability of waves, and assesses the value of wave forecasting in electricity markets. vii. Lastly, it reviews the economic assessment of wave energy projects. The scope of the thesis is broad...... and embraces subjects that can be categorised within technical and non-technical disciplines. This combination of findings leads to an overview of the wave energy field and of WEC developments. It underlines hindrances that can affect developments when WECs are commissioned and the benefits wave energy brings...

  6. Application of the Most Likely Extreme Response Method for Wave Energy Converters: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Quon, Eliot; Platt, Andrew; Yu, Yi-Hsiang; Lawson, Michael

    2016-07-01

    Extreme loads are often a key cost driver for wave energy converters (WECs). As an alternative to exhaustive Monte Carlo or long-term simulations, the most likely extreme response (MLER) method allows mid- and high-fidelity simulations to be used more efficiently in evaluating WEC response to events at the edges of the design envelope, and is therefore applicable to system design analysis. The study discussed in this paper applies the MLER method to investigate the maximum heave, pitch, and surge force of a point absorber WEC. Most likely extreme waves were obtained from a set of wave statistics data based on spectral analysis and the response amplitude operators (RAOs) of the floating body; the RAOs were computed from a simple radiation-and-diffraction-theory-based numerical model. A weakly nonlinear numerical method and a computational fluid dynamics (CFD) method were then applied to compute the short-term response to the MLER wave. Effects of nonlinear wave and floating body interaction on the WEC under the anticipated 100-year waves were examined by comparing the results from the linearly superimposed RAOs, the weakly nonlinear model, and CFD simulations. Overall, the MLER method was successfully applied. In particular, when coupled to a high-fidelity CFD analysis, the nonlinear fluid dynamics can be readily captured.

  7. Application of the Most Likely Extreme Response Method for Wave Energy Converters

    Energy Technology Data Exchange (ETDEWEB)

    Quon, Eliot; Platt, Andrew; Yu, Yi-Hsiang; Lawson, Michael

    2016-06-24

    Extreme loads are often a key cost driver for wave energy converters (WECs). As an alternative to exhaustive Monte Carlo or long-term simulations, the most likely extreme response (MLER) method allows mid- and high-fidelity simulations to be used more efficiently in evaluating WEC response to events at the edges of the design envelope, and is therefore applicable to system design analysis. The study discussed in this paper applies the MLER method to investigate the maximum heave, pitch, and surge force of a point absorber WEC. Most likely extreme waves were obtained from a set of wave statistics data based on spectral analysis and the response amplitude operators (RAOs) of the floating body; the RAOs were computed from a simple radiation-and-diffraction-theory-based numerical model. A weakly nonlinear numerical method and a computational fluid dynamics (CFD) method were then applied to compute the short-term response to the MLER wave. Effects of nonlinear wave and floating body interaction on the WEC under the anticipated 100-year waves were examined by comparing the results from the linearly superimposed RAOs, the weakly nonlinear model, and CFD simulations. Overall, the MLER method was successfully applied. In particular, when coupled to a high-fidelity CFD analysis, the nonlinear fluid dynamics can be readily captured.

  8. Characterization and Scaling of Heave Plates for Ocean Wave Energy Converters

    Science.gov (United States)

    Rosenberg, Brian; Mundon, Timothy

    2016-11-01

    Ocean waves present a tremendous, untapped source of renewable energy, capable of providing half of global electricity demand by 2040. Devices developed to extract this energy are known as wave energy converters (WECs) and encompass a wide range of designs. A somewhat common archetype is a two-body point-absorber, in which a surface float reacts against a submerged "heave" plate to extract energy. Newer WEC's are using increasingly complex geometries for the submerged plate and an emerging challenge in creating low-order models lies in accurately determining the hydrodynamic coefficients (added mass and drag) in the corresponding oscillatory flow regime. Here we present experiments in which a laboratory-scale heave plate is sinusoidally forced in translation (heave) and rotation (pitch) to characterize the hydrodynamic coefficients as functions of the two governing nondimensional parameters, Keulegan-Carpenter number (amplitude) and Reynolds number. Comparisons against CFD simulations are offered. As laboratory-scale physical model tests remain the standard for testing wave energy devices, effects and implications of scaling (with respect to a full-scale device) are also investigated.

  9. Shock waves simulated using the dual domain material point method combined with molecular dynamics

    Science.gov (United States)

    Zhang, Duan Z.; Dhakal, Tilak R.

    2017-04-01

    In this work we combine the dual domain material point method with molecular dynamics in an attempt to create a multiscale numerical method to simulate materials undergoing large deformations with high strain rates. In these types of problems, the material is often in a thermodynamically nonequilibrium state, and conventional constitutive relations or equations of state are often not available. In this method, the closure quantities, such as stress, at each material point are calculated from a molecular dynamics simulation of a group of atoms surrounding the material point. Rather than restricting the multiscale simulation in a small spatial region, such as phase interfaces, or crack tips, this multiscale method can be used to consider nonequilibrium thermodynamic effects in a macroscopic domain. This method takes the advantage that the material points only communicate with mesh nodes, not among themselves; therefore molecular dynamics simulations for material points can be performed independently in parallel. The dual domain material point method is chosen for this multiscale method because it can be used in history dependent problems with large deformation without generating numerical noise as material points move across cells, and also because of its convergence and conservation properties. To demonstrate the feasibility and accuracy of this method, we compare the results of a shock wave propagation in a cerium crystal calculated using the direct molecular dynamics simulation with the results from this combined multiscale calculation.

  10. Relationship between wave energy and free energy from pickup ions in the Comet Halley environment

    Science.gov (United States)

    Huddleston, D. E.; Johnstone, A. D.

    1992-01-01

    The free energy available from the implanted heavy ion population at Comet Halley is calculated by assuming that the initial unstable velocity space ring distribution of the ions evolves toward a bispherical shell. Ultimately this free energy adds to the turbulence in the solar wind. Upstream and downstream free energies are obtained separately for the conditions observed along the Giotto spacecraft trajectory. The results indicate that the waves are mostly upstream propagating in the solar wind frame. The total free energy density always exceeds the measured wave energy density because, as expected in the nonlinear process of ion scattering, the available energy is not all immediately released. An estimate of the amount which has been released can be obtained from the measured oxygen ion distributions and again it exceeds that observed. The theoretical analysis is extended to calculate the k spectrum of the cometary-ion-generated turbulence.

  11. Hydraulic evaluation of the Crest Wing wave energy converter

    Energy Technology Data Exchange (ETDEWEB)

    Kofoed, J.P.; Antonishen, M.

    2008-09-15

    The Crest Wing Wave Energy Converter is currently being developed by Henning Pilgaard, of WaveEnergyFyn, Denmark. It is meant to act like a carpet on the water, conforming to the shape of each wave and using that movement to generate power. The thought of making a WEC that acts like a carpet on top of the waves is not new; ongoing or past projects such as the Pelamis and Cockerel Raft were designed with this thought in mind. The real difference with the Crest Wing is that it has skirt drafts, that extend down into the water and create suction; this increases the effective mass of the WEC while minimizing the material use. Special attention was given to the design of the first and last floaters as they are meant to act as a smooth transition between wave and machine. Their purpose is to make sure that no air gets under the two middle floaters so that suction is not broken and the device continues to function well. In summary the Crest Wing functions and is able to produce power with a good overall efficiency. The configuration with relative reference PTO (Power Take Off) is superior. It has not been proven that the idea of mounting skirts on the floaters is leading to a better performance. Thus, the study leads to the conclusion that the idea of making a simple hinged raft type device is good, and it is likely that the construction cost for a device of this type can be kept down. However, the study also leaves the chance that some limited draft of skirts in combination with inlet/outlet devices, could prove beneficial. In case of further testing on this device, an effort should be made to design and construct a more easily and accurately controlled PTO model in the test setup. This could greatly improve the quality of the output of such tests. (ln)

  12. Modelling of the Overtopping Flow on the Wave Dragon Wave Energy Converter

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Pecher, Arthur; Kofoed, Jens Peter

    2010-01-01

    The Wave Dragon is a floating slack-moored Wave Energy Converter of the overtopping type, which is facing now the last phase of development before the commercial exploitation: the deployment of a full-scale demonstrator. In this phase a modelling tool allowing for accurate predictions of the perf......The Wave Dragon is a floating slack-moored Wave Energy Converter of the overtopping type, which is facing now the last phase of development before the commercial exploitation: the deployment of a full-scale demonstrator. In this phase a modelling tool allowing for accurate predictions...... of the performance of the device at different scaling ratios and locations of interest is strongly required. The overtopping, depending on the local conditions of the deployment site, is identified as the right stage to be considered in the modelling. The existing formulation of the overtopping model needs...... to be updated in order to represent more accurately the effects of the geometrical features and stability of the device and of the local conditions and nonscalable parameters on the overtopping flow. The paper analyses the conditions at which the present formulation has been established and proposes a strategy...

  13. An assessment of global ocean wave energy resources over the last 45 a

    Institute of Scientific and Technical Information of China (English)

    ZHENG Chongwei; SHAO Longtan; SHI Wenli; SU Qin; LIN Gang; LI Xunqiang; CHEN Xiaobin

    2014-01-01

    Against the background of the current world facing an energy crisis, and human beings puzzled by the prob-lems of environment and resources, developing clean energy sources becomes the inevitable choice to deal with a climate change and an energy shortage. A global ocean wave energy resource was reanalyzed by using ERA-40 wave reanalysis data 1957-2002 from European Centre for Medium-Range Weather Forecast-s (ECMWF). An effective significant wave height is defined in the development of wave energy resources (short as effective SWH), and the total potential of wave energy is exploratively calculated. Synthetically considering a wave energy density, a wave energy level probability, the frequency of the effective SWH, the stability and long-term trend of wave energy density, a swell index and a wave energy storage, global ocean wave energy resources were reanalyzed and regionalized, providing reference to the development of wave energy resources such as wave power plant location, seawater desalination, heating, pumping.

  14. Prospective comparison of liver stiffness measurements between two point wave elastography methods: Virtual ouch quantification and elastography point quantification

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Hyun Suk; Lee, Jeong Min; Yoon, Jeong Hee; Lee, Dong Ho; Chang, Won; Han, Joon Koo [Seoul National University Hospital, Seoul (Korea, Republic of)

    2016-09-15

    To prospectively compare technical success rate and reliable measurements of virtual touch quantification (VTQ) elastography and elastography point quantification (ElastPQ), and to correlate liver stiffness (LS) measurements obtained by the two elastography techniques. Our study included 85 patients, 80 of whom were previously diagnosed with chronic liver disease. The technical success rate and reliable measurements of the two kinds of point shear wave elastography (pSWE) techniques were compared by χ{sup 2} analysis. LS values measured using the two techniques were compared and correlated via Wilcoxon signed-rank test, Spearman correlation coefficient, and 95% Bland-Altman limit of agreement. The intraobserver reproducibility of ElastPQ was determined by 95% Bland-Altman limit of agreement and intraclass correlation coefficient (ICC). The two pSWE techniques showed similar technical success rate (98.8% for VTQ vs. 95.3% for ElastPQ, p = 0.823) and reliable LS measurements (95.3% for VTQ vs. 90.6% for ElastPQ, p = 0.509). The mean LS measurements obtained by VTQ (1.71 ± 0.47 m/s) and ElastPQ (1.66 ± 0.41 m/s) were not significantly different (p = 0.209). The LS measurements obtained by the two techniques showed strong correlation (r = 0.820); in addition, the 95% limit of agreement of the two methods was 27.5% of the mean. Finally, the ICC of repeat ElastPQ measurements was 0.991. Virtual touch quantification and ElastPQ showed similar technical success rate and reliable measurements, with strongly correlated LS measurements. However, the two methods are not interchangeable due to the large limit of agreement.

  15. Investigation of Wave Energy Converter Effects on Near-shore Wave Fields: Model Generation Validation and Evaluation - Kaneohe Bay HI.

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Jesse D.; Chang, Grace; Jones, Craig

    2014-09-01

    The numerical model, SWAN (Simulating WAves Nearshore) , was used to simulate wave conditions in Kaneohe Bay, HI in order to determine the effects of wave energy converter ( WEC ) devices on the propagation of waves into shore. A nested SWAN model was validated then used to evaluate a range of initial wave conditions: significant wave heights (H s ) , peak periods (T p ) , and mean wave directions ( MWD) . Differences between wave height s in the presence and absence of WEC device s were assessed at locations in shore of the WEC array. The maximum decrease in wave height due to the WEC s was predicted to be approximately 6% at 5 m and 10 m water depths. Th is occurred for model initiation parameters of H s = 3 m (for 5 m water depth) or 4 m (10 m water depth) , T p = 10 s, and MWD = 330deg . Subsequently, bottom orbital velocities were found to decrease by about 6%.

  16. Energy flux measurement from the dissipated energy in capillary wave turbulence.

    Science.gov (United States)

    Deike, Luc; Berhanu, Michael; Falcon, Eric

    2014-02-01

    We study experimentally the influence of dissipation on stationary capillary wave turbulence on the surface of a liquid by changing its viscosity. We observe that the frequency power-law scaling of the capillary spectrum departs significantly from its theoretical value when the dissipation is increased. The energy dissipated by capillary waves is also measured and found to increase nonlinearly with the mean power injected within the liquid. Here we propose an experimental estimation of the energy flux at every scale of the capillary cascade. The latter is found to be nonconstant through the scales. For fluids of low enough viscosity, we found that both capillary spectrum scalings with the frequency and the newly defined mean energy flux are in good agreement with wave turbulence theory. The Kolmogorov-Zakharov constant is then experimentally estimated and compared to its theoretical value.

  17. An Experimental Study on A Trapezoidal Pendulum Wave Energy Converter in Regular Waves

    Institute of Scientific and Technical Information of China (English)

    王冬姣; 邱守强; 叶家玮

    2015-01-01

    Experimental studies were conducted on a trapezoidal pendulum wave energy converter in regular waves. To obtain the incident wave height, the analytical method (AM) was used to separate the incident and reflected waves propagating in a wave flume by analysing wave records measured at two locations. The response amplitude operator (RAO), primary conversion efficiency and the total conversion efficiency of the wave energy converter were studied; furthermore, the power take-off damping coefficients corresponding to the load resistances in the experiment were also obtained. The findings demonstrate that the natural period for a pendulum wave energy converter is relatively large. A lower load resistance gives rise to a larger damping coefficient. The model shows relatively higher wave energy conversion efficiency in the range of 1.0-1.2 s for the incident wave period. The maximum primary conversion efficiency achieved was 55.5%, and the maximum overall conversion efficiency was 39.4%.

  18. Artificial ocean upwelling utilizing the energy of surface waves

    Science.gov (United States)

    Soloviev, Alexander

    2016-04-01

    Artificial upwelling can bring cold water from below the thermocline to the sea surface. Vershinsky, Pshenichnyy, and Soloviev (1987) developed a prototype device, utilizing the energy of surface waves to create an upward flow of water in the tube. This is a wave-inertia pump consisting of a vertical tube, a valve, and a buoy to keep the device afloat. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10 oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. A system of artificial upwelling devices can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from a deeper layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps and climatic consequences are estimated for different environmental conditions using a computational fluid dynamics model.

  19. HYDRODYNAMIC ANALYSIS OF SHORELINE OWC TYPE WAVE ENERGY CONVERTERS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A numerical model to predict the hydrodynamic performance of a shoreline-mounted wave energy converter, normally referred to as Oscillating Water Column (OWC), was established. Based on the 3D boundary integral equation method, the 3D Green's function was utilized to describe the hydrodynamic flow around the device. Using geometrical data of a wave absorber device symmetrically placed in a channel with various barrier depths, the hydrodynamic efficiencies were calculated for regular waves. The results were the ncompared with analytical results published elsewhere Malmo[8] . And the comparison is shown to be good, thus validating the proposed numerical model. Furthermore, extensive experiments were also made in a wave tank with a 1:12 scale model of an OWC device of different geometrical configurations. The experimental measurements were compared with calculations using the newly developed numerical model. The comparison, which is also shown to be satisfactory, provides further support of the correctness and the accuracy of the numerical method presented in the paper.

  20. Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter

    Energy Technology Data Exchange (ETDEWEB)

    Tom, Nathan M.; Yu, Yi-Hsiang; Wright, Alan D.; Lawson, Michael

    2016-06-24

    The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of the controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.

  1. Reference Model 6 (RM6): Oscillating Wave Energy Converter.

    Energy Technology Data Exchange (ETDEWEB)

    Bull, Diana L; Smith, Chris; Jenne, Dale Scott; Jacob, Paul; Copping, Andrea; Willits, Steve; Fontaine, Arnold; Brefort, Dorian; Gordon, Margaret Ellen; Copeland, Robert; Jepsen, Richard Alan

    2014-10-01

    This report is an addendum to SAND2013-9040: Methodology for Design and Economic Analysis of Marine Energy Conversion (MEC) Technologies. This report describes an Oscillating Water Column Wave Energy Converter reference model design in a complementary manner to Reference Models 1-4 contained in the above report. In this report, a conceptual design for an Oscillating Water Column Wave Energy Converter (WEC) device appropriate for the modeled reference resource site was identified, and a detailed backward bent duct buoy (BBDB) device design was developed using a combination of numerical modeling tools and scaled physical models. Our team used the methodology in SAND2013-9040 for the economic analysis that included costs for designing, manufacturing, deploying, and operating commercial-scale MEC arrays, up to 100 devices. The methodology was applied to identify key cost drivers and to estimate levelized cost of energy (LCOE) for this RM6 Oscillating Water Column device in dollars per kilowatt-hour ($/kWh). Although many costs were difficult to estimate at this time due to the lack of operational experience, the main contribution of this work was to disseminate a detailed set of methodologies and models that allow for an initial cost analysis of this emerging technology. This project is sponsored by the U.S. Department of Energy's (DOE) Wind and Water Power Technologies Program Office (WWPTO), within the Office of Energy Efficiency & Renewable Energy (EERE). Sandia National Laboratories, the lead in this effort, collaborated with partners from National Laboratories, industry, and universities to design and test this reference model.

  2. Wind, Wave, and Tidal Energy Without Power Conditioning

    Science.gov (United States)

    Jones, Jack A.

    2013-01-01

    Most present wind, wave, and tidal energy systems require expensive power conditioning systems that reduce overall efficiency. This new design eliminates power conditioning all, or nearly all, of the time. Wind, wave, and tidal energy systems can transmit their energy to pumps that send high-pressure fluid to a central power production area. The central power production area can consist of a series of hydraulic generators. The hydraulic generators can be variable displacement generators such that the RPM, and thus the voltage, remains constant, eliminating the need for further power conditioning. A series of wind blades is attached to a series of radial piston pumps, which pump fluid to a series of axial piston motors attached to generators. As the wind is reduced, the amount of energy is reduced, and the number of active hydraulic generators can be reduced to maintain a nearly constant RPM. If the axial piston motors have variable displacement, an exact RPM can be maintained for all, or nearly all, wind speeds. Analyses have been performed that show over 20% performance improvements with this technique over conventional wind turbines

  3. Equilibrium distribution of the wave energy in a carbyne chain

    Science.gov (United States)

    Kovriguine, D. A.; Nikitenkova, S. P.

    2016-03-01

    The steady-state energy distribution of thermal vibrations at a given ambient temperature has been investigated based on a simple mathematical model that takes into account central and noncentral interactions between carbon atoms in a one-dimensional carbyne chain. The investigation has been performed using standard asymptotic methods of nonlinear dynamics in terms of the classical mechanics. In the first-order nonlinear approximation, there have been revealed resonant wave triads that are formed at a typical nonlinearity of the system under phase matching conditions. Each resonant triad consists of one longitudinal and two transverse vibration modes. In the general case, the chain is characterized by a superposition of similar resonant triplets of different spectral scales. It has been found that the energy equipartition of nonlinear stationary waves in the carbyne chain at a given temperature completely obeys the standard Rayleigh-Jeans law due to the proportional amplitude dispersion. The possibility of spontaneous formation of three-frequency envelope solitons in carbyne has been demonstrated. Heat in the form of such solitons can propagate in a chain of carbon atoms without diffusion, like localized waves.

  4. Floating attenuator wave energy device: Wavegen HYDRA project

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    This report describes research funded by the Department of Trade and Industry (DTI) into the feasibility of developing and constructing a floating attenuator wave energy device known as HYDRA following initial studies by Wavegen. HYDRA is a floating externally tensioned articulated raft wave energy generator based on work by Professor FJM Farley and colleagues during the 1980s. The project's first four work tasks confirmed the theoretical potential of the device but also highlighted significant practical problems in translating that potential into a viable design. It was therefore decided not to proceed further, i.e. not to construct and test a prototype device. The report provides a general description of the device and describes the results of the initial analysis and the first series of model tests. It then discusses device design and component testing and explains the methodology for determining device performance at a particular site and mathematical modelling of a one-third scale device. To help future research and development programmes, the report emphasises the generic problems associated with the development of wave devices.

  5. 75 FR 14206 - FPL Energy Point Beach, LLC; Point Beach Nuclear Plant, Units 1 and 2; Environmental Assessment...

    Science.gov (United States)

    2010-03-24

    ... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION [Docket Nos. 50-266 And 50-301; NRC-2010-0123 FPL Energy Point Beach, LLC; Point Beach Nuclear Plant, Units 1 and 2; Environmental Assessment and Finding of No Significant Impact The U.S. Nuclear...

  6. Application of the nudged elastic band method to the point-to-point radio wave ray tracing in IRI modeled ionosphere

    Science.gov (United States)

    Nosikov, I. A.; Klimenko, M. V.; Bessarab, P. F.; Zhbankov, G. A.

    2017-07-01

    Point-to-point ray tracing is an important problem in many fields of science. While direct variational methods where some trajectory is transformed to an optimal one are routinely used in calculations of pathways of seismic waves, chemical reactions, diffusion processes, etc., this approach is not widely known in ionospheric point-to-point ray tracing. We apply the Nudged Elastic Band (NEB) method to a radio wave propagation problem. In the NEB method, a chain of points which gives a discrete representation of the radio wave ray is adjusted iteratively to an optimal configuration satisfying the Fermat's principle, while the endpoints of the trajectory are kept fixed according to the boundary conditions. Transverse displacements define the radio ray trajectory, while springs between the points control their distribution along the ray. The method is applied to a study of point-to-point ionospheric ray tracing, where the propagation medium is obtained with the International Reference Ionosphere model taking into account traveling ionospheric disturbances. A 2-dimensional representation of the optical path functional is developed and used to gain insight into the fundamental difference between high and low rays. We conclude that high and low rays are minima and saddle points of the optical path functional, respectively.

  7. Evaluating Energy based DDOS Attacks using Cosmic FFP and Energy Points

    Directory of Open Access Journals (Sweden)

    P.C. Senthil Mahesh

    2014-04-01

    Full Text Available The aim of the study is to improve security and identify DDOS attacks. Security should be considered affront during software development as millions of dollars are lost due to security breaches in software. There are many kinds of security breaches and of these DDOS attacks plays a leading role and as such it is vital that new techniques be identified to combat this rising menace. In this study a new sizing techniques called energy Points are used to identify the energy based DDOS attacks.

  8. Wave-mean flow interaction and its relationship with the atmospheric energy cycle with diabatic heating

    Institute of Scientific and Technical Information of China (English)

    DUAN Anmin; WU Guoxiong

    2005-01-01

    Based on the traditional theory of wave mean flow interaction, an improved quasi-geostrophic Eliassen-Palm flux with diabatic heating included is deduced. It is shown that there exists an intrinsic relation between the atmospheric energy cycle derived by Lorenz and the wave energy transfer derived by Eliassen and Palm. From this relation it becomes clear that the energy propagation process of large-scale stationary wave is indeed a part of Lorenz energy cycle, and the energy transform from mean flow to wave equals the global mass integral of the divergence of local wave energy flux or the global integral of local wave energy. The diagnostic results by using NCEP/NCAR reanalysis data suggest that the classical adiabatic Eliassen-Palm flux relation can present only the wintertime wave energy transformation. For other seasons, however, the diabatic effect must be taken into account.

  9. Guided wave radiation from a point source in the proximity of a pipe bend

    Science.gov (United States)

    Brath, A. J.; Simonetti, F.; Nagy, P. B.; Instanes, G.

    2014-02-01

    Throughout the oil and gas industry corrosion and erosion damage monitoring play a central role in managing asset integrity. Recently, the use of guided wave technology in conjunction with tomography techniques has provided the possibility of obtaining point-by-point maps of wall thickness loss over the entire volume of a pipeline section between two ring arrays of ultrasonic transducers. However, current research has focused on straight pipes while little work has been done on pipe bends which are also the most susceptible to developing damage. Tomography of the bend is challenging due to the complexity and computational cost of the 3-D elastic model required to accurately describe guided wave propagation. To overcome this limitation, we introduce a 2-D anisotropic inhomogeneous acoustic model which represents a generalization of the conventional unwrapping used for straight pipes. The shortest-path ray-tracing method is then applied to the 2-D model to compute ray paths and predict the arrival times of the fundamental flexural mode, A0, excited by a point source on the straight section of pipe entering the bend and detected on the opposite side. Good agreement is found between predictions and experiments performed on an 8" diameter (D) pipe with 1.5 D bend radius. The 2-D model also reveals the existence of an acoustic lensing effect which leads to a focusing phenomenon also confirmed by the experiments. The computational efficiency of the 2-D model makes it ideally suited for tomography algorithms.

  10. Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals.

    Science.gov (United States)

    Zhang, Y; Huang, S L; Wang, S; Zhao, W

    2016-05-01

    The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert-Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of wave detection signals.

  11. Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals

    Science.gov (United States)

    Zhang, Y.; Huang, S. L.; Wang, S.; Zhao, W.

    2016-05-01

    The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert-Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.

  12. Wave energy absorption by a floating air bag

    CERN Document Server

    Kurniawan, A; Greaves, D M; Hann, M; Farley, F J M

    2016-01-01

    A floating air bag, ballasted in water, expands and contracts as it heaves under wave action. Connecting the bag to a secondary volume via a turbine transforms the bag into a device capable of generating useful energy from the waves. Small-scale measurements of the device reveal some interesting properties, which are successfully predicted numerically. Owing to its compressibility, the device can have a resonance period longer than that of a rigid device of the same shape and size, without any phase control. Furthermore, varying the amount of air in the bag is found to change its shape and hence its dynamic response, while varying the turbine damping or the air volume ratio changes the dynamic response without changing the shape.

  13. Technical Submission Form: Technical Specification of a Wave Energy Farm.

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Jesse D.; Kim Nielsen; Ben Kennedy; Bull, Diana L; Costello, Ronan Patrick; Jochem Weber

    2017-04-01

    The Wave - SPARC project developed the Technology Performance Level (TPL) assessment procedure based on a rigorous Systems Engineering exercise. The TPL assessment allows a whole system evaluation of Wave Energy Conversion Technology by measuring it against the requirements determined through the Systems Engineering exercise. The TPL assessment is intended to be useful in technology evaluation; in technology innovation; in allocation of public or priva te investment, and; in making equipment purchasing decisions. This Technical Submission Form (TSF) serves the purpose of collecting relevant and complete information, in a technology agnostic way, to allow TPL assessment s to be made by third party assessor s. The intended usage of this document is that the organization or people that are performing the role of developers or promoters of a particular technology will use this form to provide the information necessary for the organization or people who are perf orming the assessor role to use the TPL assessment.

  14. Licensing and Environmental Issues of Wave Energy Projects

    DEFF Research Database (Denmark)

    Neumann, Frank; Tedd, James; Prado, Miguel

    2006-01-01

    The major non-technical barrier for large-scale wave energy implementation is the wide range of licensing issues and potential environmental concerns, in addition to significant National/regional differences in licensing procedures and permit requirements. Whereas some pilot plants have had...... as concerning ocean space use and environmental concerns. Despite recent efforts to streamline European EIA (Environmental Impact Assessment) in general, potential project developers are far from having a clear view of present and future requirements concerning these barriers on a trans-national level...... pilot plants and exemplary presents the ongoing permitting process of the Wave Dragon in Wales. Comments on future park-scale application issues are made based on the present situation in different countries....

  15. Energy Harvesting From Sea Waves With Consideration of Airy and JONSWAP Theory and Optimization of Energy Harvester Parameters

    Institute of Scientific and Technical Information of China (English)

    Hadi Mirab; Reza Fathi; Vahid Jahangiri; Mir Mohammad Ettefagh; Reza Hassannejad

    2015-01-01

    One of the new methods for powering low-power electronic devices at sea is a wave energy harvesting system. In this method, piezoelectric material is employed to convert the mechanical energy of sea waves into electrical energy. The advantage of this method is based on avoiding a battery charging system. Studies have been done on energy harvesting from sea waves, however, considering energy harvesting with random JONSWAP wave theory, then determining the optimum values of energy harvested is new. This paper does that by implementing the JONSWAP wave model, calculating produced power, and realistically showing that output power is decreased in comparison with the more simple Airy wave model. In addition, parameters of the energy harvester system are optimized using a simulated annealing algorithm, yielding increased produced power.

  16. Holocene reef development where wave energy reduces accommodation

    Science.gov (United States)

    Grossman, Eric E.; Fletcher, Charles H.

    2004-01-01

    Analyses of 32 drill cores obtained from the windward reef of Kailua Bay, Oahu, Hawaii, indicate that high wave energy significantly reduced accommodation space for reef development in the Holocene and produced variable architecture because of the combined influence of sea-level history and wave exposure over a complex antecedent topography. A paleostream valley within the late Pleistocene insular limestone shelf provided accommodation space for more than 11 m of vertical accretion since sea level flooded the bay 8000 yr BP. Virtually no net accretion (pile-up of fore-reef-derived rubble (rudstone) and sparse bindstone, and (3) a final stage of catch-up bindstone accretion in depths > 6 m. Coral framestone accreted at rates of 2.5-6.0 mm/yr in water depths > 11 m during the early Holocene; it abruptly terminated at ~4500 yr BP because of wave scour as sea level stabilized. More than 4 m of rudstone derived from the upper fore reef accreted at depths of 6 to 13 m below sea level between 4000 and 1500 yr BP coincident with late Holocene relative sea-level fall. Variations in the thickness, composition, and age of these reef facies across spatial scales of 10-1000 m within Kailua Bay illustrate the importance of antecedent topography and wave-related stress in reducing accommodation space for reef development set by sea level. Although accommodation space of 6 to 17 m has existed through most of the Holocene, the Kailua reef has been unable to catch up to sea level because of persistent high wave stress.

  17. Energy scaling of terahertz-wave parametric sources.

    Science.gov (United States)

    Tang, Guanqi; Cong, Zhenhua; Qin, Zengguang; Zhang, Xingyu; Wang, Weitao; Wu, Dong; Li, Ning; Fu, Qiang; Lu, Qingming; Zhang, Shaojun

    2015-02-23

    Terahertz-wave parametric oscillators (TPOs) have advantages of room temperature operation, wide tunable range, narrow line-width, good coherence. They have also disadvantage of small pulse energy. In this paper, several factors preventing TPOs from generating high-energy THz pulses and the corresponding solutions are analyzed. A scheme to generate high-energy THz pulses by using the combination of a TPO and a Stokes-pulse-injected terahertz-wave parametric generator (spi-TPG) is proposed and demonstrated. A TPO is used as a source to generate a seed pulse for the surface-emitted spi-TPG. The time delay between the pump and Stokes pulses is adjusted to guarantee they have good temporal overlap. The pump pulses have a large pulse energy and a large beam size. The Stokes beam is enlarged to make its size be larger than the pump beam size to have a large effective interaction volume. The experimental results show that the generated THz pulse energy from the spi-TPG is 1.8 times as large as that obtained from the TPO for the same pumping pulse energy density of 0.90 J/cm(2) and the same pumping beam size of 3.0 mm. When the pumping beam sizes are 5.0 and 7.0 mm, the enhancement times are 3.7 and 7.5, respectively. The spi-TPG here is similar to a difference frequency generator; it can also be used as a Stokes pulse amplifier.

  18. Primordial blackholes and gravitational waves for an inflection-point model of inflation

    Energy Technology Data Exchange (ETDEWEB)

    Choudhury, Sayantan [Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 B.T. Road, Kolkata 700 108 (India); Mazumdar, Anupam [Consortium for Fundamental Physics, Physics Department, Lancaster University, LA1 4YB (United Kingdom)

    2014-06-02

    In this article we provide a new closed relationship between cosmic abundance of primordial gravitational waves and primordial blackholes that originated from initial inflationary perturbations for inflection-point models of inflation where inflation occurs below the Planck scale. The current Planck constraint on tensor-to-scalar ratio, running of the spectral tilt, and from the abundance of dark matter content in the universe, we can deduce a strict bound on the current abundance of primordial blackholes to be within a range, 9.99712×10{sup −3}<Ω{sub PBH}h{sup 2}<9.99736×10{sup −3}.

  19. Primordial blackholes and gravitational waves for an inflection-point model of inflation

    Science.gov (United States)

    Choudhury, Sayantan; Mazumdar, Anupam

    2014-06-01

    In this article we provide a new closed relationship between cosmic abundance of primordial gravitational waves and primordial blackholes that originated from initial inflationary perturbations for inflection-point models of inflation where inflation occurs below the Planck scale. The current Planck constraint on tensor-to-scalar ratio, running of the spectral tilt, and from the abundance of dark matter content in the universe, we can deduce a strict bound on the current abundance of primordial blackholes to be within a range, 9.99712 ×10-3 <ΩPBHh2 < 9.99736 ×10-3.

  20. A Monolithic Double-balanced Upconverter for millimeter-wave Point-to-Multipoint Distribution Systems

    OpenAIRE

    Ang, K S; Robertson, I.D.

    2000-01-01

    The design and performance of a monolithic double-balanced upconverter for mm-wave point-to- multipoint distribution systems are presented. Individual building blocks including the LO /RF balun, IF balun,LO /RF power amplifier,and the double- balanced mixer are also fabricated and tested.The complete upconverter,measuring 3x3.2mm,upconverts the 3 -5GHz IF to 40.5 -43.5GHz band with 20 dBm output power.

  1. Networks of triboelectric nanogenerators for harvesting water wave energy: a potential approach toward blue energy.

    Science.gov (United States)

    Chen, Jun; Yang, Jin; Li, Zhaoling; Fan, Xing; Zi, Yunlong; Jing, Qingshen; Guo, Hengyu; Wen, Zhen; Pradel, Ken C; Niu, Simiao; Wang, Zhong Lin

    2015-03-24

    With 70% of the earth's surface covered with water, wave energy is abundant and has the potential to be one of the most environmentally benign forms of electric energy. However, owing to lack of effective technology, water wave energy harvesting is almost unexplored as an energy source. Here, we report a network design made of triboelectric nanogenerators (TENGs) for large-scale harvesting of kinetic water energy. Relying on surface charging effect between the conventional polymers and very thin layer of metal as electrodes for each TENG, the TENG networks (TENG-NW) that naturally float on the water surface convert the slow, random, and high-force oscillatory wave energy into electricity. On the basis of the measured output of a single TENG, the TENG-NW is expected to give an average power output of 1.15 MW from 1 km(2) surface area. Given the compelling features, such as being lightweight, extremely cost-effective, environmentally friendly, easily implemented, and capable of floating on the water surface, the TENG-NW renders an innovative and effective approach toward large-scale blue energy harvesting from the ocean.

  2. Experimental Validation of a Theory for a Variable Resonant Frequency Wave Energy Converter (VRFWEC)

    Science.gov (United States)

    Park, Minok; Virey, Louis; Chen, Zhongfei; Mäkiharju, Simo

    2016-11-01

    A point absorber wave energy converter designed to adapt to changes in wave frequency and be highly resilient to harsh conditions, was tested in a wave tank for wave periods from 0.8 s to 2.5 s. The VRFWEC consists of a closed cylindrical floater containing an internal mass moving vertically and connected to the floater through a spring system. The internal mass and equivalent spring constant are adjustable and enable to match the resonance frequency of the device to the exciting wave frequency, hence optimizing the performance. In a full scale device, a Permanent Magnet Linear Generator will convert the relative motion between the internal mass and the floater into electricity. For a PMLG as described in Yeung et al. (OMAE2012), the electromagnetic force proved to cause dominantly linear damping. Thus, for the present preliminary study it was possible to replace the generator with a linear damper. While the full scale device with 2.2 m diameter is expected to generate O(50 kW), the prototype could generate O(1 W). For the initial experiments the prototype was restricted to heave motion and data compared to predictions from a newly developed theoretical model (Chen, 2016).

  3. Advanced, High Power, Next Scale, Wave Energy Conversion Device

    Energy Technology Data Exchange (ETDEWEB)

    Mekhiche, Mike [Principal Investigator; Dufera, Hiz [Project Manager; Montagna, Deb [Business Point of Contact

    2012-10-29

    The project conducted under DOE contract DE‐EE0002649 is defined as the Advanced, High Power, Next Scale, Wave Energy Converter. The overall project is split into a seven‐stage, gated development program. The work conducted under the DOE contract is OPT Stage Gate III work and a portion of Stage Gate IV work of the seven stage product development process. The project effort includes Full Concept Design & Prototype Assembly Testing building on our existing PowerBuoy technology to deliver a device with much increased power delivery. Scaling‐up from 150kW to 500kW power generating capacity required changes in the PowerBuoy design that addressed cost reduction and mass manufacturing by implementing a Design for Manufacturing (DFM) approach. The design changes also focused on reducing PowerBuoy Installation, Operation and Maintenance (IO&M) costs which are essential to reducing the overall cost of energy. In this design, changes to the core PowerBuoy technology were implemented to increase capability and reduce both CAPEX and OPEX costs. OPT conceptually envisaged moving from a floating structure to a seabed structure. The design change from a floating structure to seabed structure would provide the implementation of stroke‐ unlimited Power Take‐Off (PTO) which has a potential to provide significant power delivery improvement and transform the wave energy industry if proven feasible.

  4. High-resolution wave number spectrum using multi-point measurements in space – the Multi-point Signal Resonator (MSR technique

    Directory of Open Access Journals (Sweden)

    Y. Narita

    2011-02-01

    Full Text Available A new analysis method is presented that provides a high-resolution power spectrum in a broad wave number domain based on multi-point measurements. The analysis technique is referred to as the Multi-point Signal Resonator (MSR and it benefits from Capon's minimum variance method for obtaining the proper power spectral density of the signal as well as the MUSIC algorithm (Multiple Signal Classification for considerably reducing the noise part in the spectrum. The mathematical foundation of the analysis method is presented and it is applied to synthetic data as well as Cluster observations of the interplanetary magnetic field. Using the MSR technique for Cluster data we find a wave in the solar wind propagating parallel to the mean magnetic field with relatively small amplitude, which is not identified by the Capon spectrum. The Cluster data analysis shows the potential of the MSR technique for studying waves and turbulence using multi-point measurements.

  5. Coupled Mooring Analyses for the WEC-Sim Wave Energy Converter Design Tool: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Sirnivas, Senu; Yu, Yi-Hsiang; Hall, Matthew; Bosma, Bret

    2016-07-01

    A wave-energy-converter-specific time-domain modeling method (WEC-Sim) was coupled with a lumped-mass-based mooring model (MoorDyn) to improve its mooring dynamics modeling capability. This paper presents a verification and validation study on the coupled numerical method. First, a coupled model was built to simulate a 1/25 model scale floating power system connected to a traditional three-point catenary mooring with an angle of 120 between the lines. The body response and the tension force on the mooring lines at the fairlead in decay tests and under regular and irregular waves were examined. To validate and verify the coupled numerical method, the simulation results were compared to the measurements from a wave tank test and a commercial code (OrcaFlex). Second, a coupled model was built to simulate a two-body point absorber system with a chain-connected catenary system. The influence of the mooring connection on the point absorber was investigated. Overall, the study showed that the coupling of WEC-Sim and the MoorDyn model works reasonably well for simulating a floating system with practical mooring designs and predicting the corresponding dynamic loads on the mooring lines. Further analyses on improving coupling efficiency and the feasibility of applying the numerical method to simulate WEC systems with more complex mooring configuration are still needed.

  6. Coupled Mooring Analyses for the WEC-Sim Wave Energy Converter Design Tool

    Energy Technology Data Exchange (ETDEWEB)

    Sirnivas, Senu; Yu, Yi-Hsiang; Hall, Matthew; Bosma, Bret

    2016-06-24

    A wave-energy-converter-specific time-domain modeling method (WEC-Sim) was coupled with a lumped-mass-based mooring model (MoorDyn) to improve its mooring dynamics modeling capability. This paper presents a verification and validation study on the coupled numerical method. First, a coupled model was built to simulate a 1/25 model scale floating power system connected to a traditional three-point catenary mooring with an angle of 120 between the lines. The body response and the tension force on the mooring lines at the fairlead in decay tests and under regular and irregular waves were examined. To validate and verify the coupled numerical method, the simulation results were compared to the measurements from a wave tank test and a commercial code (OrcaFlex). Second, a coupled model was built to simulate a two-body point absorber system with a chain-connected catenary system. The influence of the mooring connection on the point absorber was investigated. Overall, the study showed that the coupling of WEC-Sim and the MoorDyn model works reasonably well for simulating a floating system with practical mooring designs and predicting the corresponding dynamic loads on the mooring lines. Further analyses on improving coupling efficiency and the feasibility of applying the numerical method to simulate WEC systems with more complex mooring configuration are still needed.

  7. Directional wave and temperature data from seven buoys at Point Reyes, CA, 1996-2002 (NODC Accession 0000760)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wave data were collected from 7 buoys in Point Reyes, California, from 06 December 1996 to 25 July 2002. Data were collected as part of the Coastal Data Information...

  8. Electromagnetic Lead Screw for Potential Wave Energy Application

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Wu, Weimin

    2014-01-01

    This paper presents a new type electromagnetic lead screw (EMLS) intended for wave energy application. Similar to the mechanical lead screw, this electromagnetic version can transfer slow linear motion to high-rotational motion, offering gearing effects. Compared with the existing pure magnetic...... lead screw (MLS) employing permanent magnets only, the new EMLS proposed uses dc current to provide the required helical-shape magnetic field, offering a much simpler, robust structure compared with the MLS. The working principle and the performances of this EMLS are analyzed in this paper. Comparison...

  9. Different Reliability Assessment Approaches for Wave Energy Converters

    DEFF Research Database (Denmark)

    Ambühl, Simon; Kramer, Morten Mejlhede; Sørensen, John Dalsgaard

    2015-01-01

    Reliability assessments are of importance for wave energy converters (WECs) due to the fact that accessibility might be limited in case of failure and maintenance. These failure rates can be adapted by reliability considerations. There are two different approaches to how reliability can...... be estimated: the so-called classical reliability theory and the probabilistic reliability theory. The classical reliability theory is often used for failure rate estimations of mechanical and electrical components, whereas the probabilistic reliability theory is commonly used for structural components...

  10. Reference Model 5 (RM5): Oscillating Surge Wave Energy Converter

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Y. H. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Jenne, D. S. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Thresher, R. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Copping, A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Geerlofs, S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hanna, L. A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-01-01

    This report is an addendum to SAND2013-9040: Methodology for Design and Economic Analysis of Marine Energy Conversion (MEC) Technologies. This report describes an Oscillating Water Column Wave Energy Converter (OSWEC) reference model design in a complementary manner to Reference Models 1-4 contained in the above report. A conceptual design for a taut moored oscillating surge wave energy converter was developed. The design had an annual electrical power of 108 kilowatts (kW), rated power of 360 kW, and intended deployment at water depths between 50 m and 100 m. The study includes structural analysis, power output estimation, a hydraulic power conversion chain system, and mooring designs. The results were used to estimate device capital cost and annual operation and maintenance costs. The device performance and costs were used for the economic analysis, following the methodology presented in SAND2013-9040 that included costs for designing, manufacturing, deploying, and operating commercial-scale MEC arrays up to 100 devices. The levelized cost of energy estimated for the Reference Model 5 OSWEC, presented in this report, was for a single device and arrays of 10, 50, and 100 units, and it enabled the economic analysis to account for cost reductions associated with economies of scale. The baseline commercial levelized cost of energy estimate for the Reference Model 5 device in an array comprised of 10 units is $1.44/kilowatt-hour (kWh), and the value drops to approximately $0.69/kWh for an array of 100 units.

  11. Stable long-time semiclassical description of zero-point energy in high-dimensional molecular systems.

    Science.gov (United States)

    Garashchuk, Sophya; Rassolov, Vitaly A

    2008-07-14

    Semiclassical implementation of the quantum trajectory formalism [J. Chem. Phys. 120, 1181 (2004)] is further developed to give a stable long-time description of zero-point energy in anharmonic systems of high dimensionality. The method is based on a numerically cheap linearized quantum force approach; stabilizing terms compensating for the linearization errors are added into the time-evolution equations for the classical and nonclassical components of the momentum operator. The wave function normalization and energy are rigorously conserved. Numerical tests are performed for model systems of up to 40 degrees of freedom.

  12. Low frequency sonic waves assisted cloud point extraction of polyhydroxyalkanoate from Cupriavidus necator.

    Science.gov (United States)

    Murugesan, Sivananth; Iyyaswami, Regupathi

    2017-08-15

    Low frequency sonic waves, less than 10kHz were introduced to assist cloud point extraction of polyhydroxyalkanoate from Cupriavidus necator present within the crude broth. Process parameters including surfactant system variables and sonication parameters were studied for their effect on extraction efficiency. Introduction of low frequency sonic waves assists in the dissolution of microbial cell wall by the surfactant micelles and release of cellular content, polyhydroxyalkanoate granules released were encapsulated by the micelle core which was confirmed by crotonic acid assay. In addition, sonic waves resulted in the separation of homogeneous surfactant and broth mixture into two distinct phases, top aqueous phase and polyhydroxyalkanoate enriched bottom surfactant rich phase. Mixed surfactant systems showed higher extraction efficiency compared to that of individual Triton X-100 concentrations, owing to increase in the hydrophobicity of the micellar core and its interaction with polyhydroxyalkanoate. Addition of salts to the mixed surfactant system induces screening of charged surfactant head groups and reduces inter-micellar repulsion, presence of ammonium ions lead to electrostatic repulsion and weaker cation sodium enhances the formation of micellar network. Addition of polyethylene glycol 8000 resulted in increasing interaction with the surfactant tails of the micelle core there by reducing the purity of polyhydroxyalkanoate. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Modelling and Testing of Wave Dragon Wave Energy Converter Towards Full Scale Deployment

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano

    -commercial stage in which it has proven difficult to secure the necessary funding for the deployment of a full-scale demonstrator unit. The work presented aims at easing this process, by increasing public and scientific knowledge of the device, as well as by showing the latest progress in its development. Research....... This is mainly due to the development of an updated overtopping model specifically suited to Wave Dragon, which allows greater quality to predictions of the primary energy absorption of the device compared to previous versions. At the same time an equitable approach has been described and used in the performance......, the research has also provided a deeper insight into the physics of the overtopping process by individually assessing the influence of related device configuration and wave features, which goes beyond the present application and may be used for other overtopping WECs as well. Comprehensive analysis...

  14. Performance Assessment of the Wave Dragon Wave Energy Converter Based on the EquiMar Methodology

    DEFF Research Database (Denmark)

    Parmeggiani, Stefano; Chozas, Julia Fernandez; Pecher, Arthur

    2011-01-01

    At the present pre-commercial phase of the wave energy sector, device developers are called to provide reliable estimates on power performance and production at possible deployment locations. The EU EquiMar project has proposed a novel approach, where the performance assessment is based mainly...... on experimental data deriving from sea trials rather than solely on numerical predictions. The study applies this methodology to evaluate the performance of Wave Dragon at two locations in the North Sea, based on the data acquired during the sea trials of a 1:4.5 scale prototype. Indications about power...... performance and production of the device at the target locations, as well as on the applicability of the methodology, are provided....

  15. Numerical Forecasting Experiment of the Wave Energy Resource in the China Sea

    Directory of Open Access Journals (Sweden)

    Chong Wei Zheng

    2016-01-01

    Full Text Available The short-term forecasting of wave energy is important to provide guidance for the electric power operation and power transmission system and to enhance the efficiency of energy capture and conversion. This study produced a numerical forecasting experiment of the China Sea wave energy using WAVEWATCH-III (WW3, the latest version 4.18 wave model driven by T213 (WW3-T213 and T639 (WW3-T639 wind data separately. Then the WW3-T213 and WW3-T639 were verified and compared to build a short-term wave energy forecasting structure suited for the China Sea. Considering the value of wave power density (WPD, “wave energy rose,” daily and weekly total storage and effective storage of wave energy, this study also designed a series of short-term wave energy forecasting productions. Results show that both the WW3-T213 and WW3-T639 exhibit a good skill on the numerical forecasting of the China Sea WPD, while the result of WW3-T639 is much better. Judging from WPD and daily and weekly total storage and effective storage of wave energy, great wave energy caused by cold airs was found. As there are relatively frequent cold airs in winter, early spring, and later autumn in the China Sea and the surrounding waters, abundant wave energy ensues.

  16. Numerical comparison between deep water and intermediate water depth expressions applied to a wave energy converter

    Directory of Open Access Journals (Sweden)

    Pedro Beirão

    2015-09-01

    Full Text Available The energy that can be captured from the sea waves and converted into electricity should be seen as a contribution to decrease the excessive dependency and growing demand of fossil fuels. Devices suitable to harness this kind of renewable energy source and convert it into electricity—wave energy converters (WECs—are not yet commercially competitive. There are several types of WECs, with different designs and working principles. One possible classification is their distance to the shoreline and thus their depth. Near-shore devices are one of them since they are typically deployed at intermediate water depth (IWD. The selection of the WEC deployment site should be a balance between several parameters; water depth is one of them. Another way of classifying WECs is grouping them by their geometry, size and orientation. Considering a near-shore WEC belonging to the floating point category, this paper is focused on the numerical study about the differences arising in the power captured from the sea waves when the typical deep water (DW assumption is compared with the more realistic IWD consideration. Actually, the production of electricity will depend, among other issues, on the depth of the deployment site. The development of a dynamic model including specific equations for the usual DW assumption as well as for IWD is also described. Derived equations were used to build a time domain simulator (TDS. Numerical results were obtained by means of simulations performed using the TDS. The objective is to simulate the dynamic behavior of the WEC due to the action of sea waves and to characterize the wave power variations according with the depth of the deployment site.

  17. Potential use of point shear wave elastography for the pancreas: A single center prospective study

    Energy Technology Data Exchange (ETDEWEB)

    Kawada, Natsuko, E-mail: kawada-na@mc.pref.osaka.jp [Department of Pathology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi, Higashinari, Osaka 537-8511 (Japan); Department of Gastroenterology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa 920-0293 (Japan); Tanaka, Sachiko, E-mail: sachi686@cocoa.plala.or.jp [Osaka Center for Cancer and Cardiovascular Disease Prevention, 1-6-107, Morinomiya, Johtoh, Osaka 536-8588 (Japan); Uehara, Hiroyuki, E-mail: uehara-hi@mc.pref.osaka.jp [Department of Gastroenterology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi, Higashinari, Osaka 537-8511 (Japan); Ohkawa, Kazuyoshi, E-mail: okawa-ka@mc.pref.osaka.jp [Department of Gastroenterology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi, Higashinari, Osaka 537-8511 (Japan); Yamai, Takuo, E-mail: yamai-ta@mc.pref.osaka.jp [Department of Gastroenterology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi, Higashinari, Osaka 537-8511 (Japan); Takada, Ryoji, E-mail: takada-ry@mc.pref.osaka.jp [Department of Gastroenterology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi, Higashinari, Osaka 537-8511 (Japan); Shiroeda, Hisakazu, E-mail: shiroeda@kanazawa-med.ac.jp [Department of Gastroenterology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa 920-0293 (Japan); Arisawa, Tomiyasu, E-mail: tarisawa@kanazawa-med.ac.jp [Department of Gastroenterology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa 920-0293 (Japan); Tomita, Yasuhiko, E-mail: tomota-ya@mc.pref.osaka.jp [Department of Pathology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi, Higashinari, Osaka 537-8511 (Japan)

    2014-04-15

    Aim: Clinical use of point shear wave elastography for the liver has been established, however, few studies demonstrated its usefulness for the pancreas. A prospective study was conducted to clarify its feasibility for the pancreas and its usefulness for the identification of high risk group for pancreatic cancer. Patients and methods: Consecutive eighty-five patients underwent point shear wave elastography for the pancreas. The success rate of shear wave velocity (SWV) measurement, that is the number of successful measurements over total 10 measurements, was recorded. The SWV of the pancreas measured at non-tumorous area was compared between patients with and without pancreatic cancer. Factors associated with high SWV were determined by logistic regression model. Results: Sixty patients were included, of these 18 had pancreatic cancer. The success rate of 100% was achieved at the head, the body and the tail of the pancreas in 80%, 83%, and 68% of the patients, respectively. The success rate of ≥80% was achieved in 100%, 100%, and 96% of the patients, respectively. Although mean SWV of the pancreas harboring pancreatic cancer tended to be higher compared with that of the pancreas without cancer (1.51 ± 0.45 m/s vs 1.43 ± 0.28 m/s), they did not reach statistical significance. Multivariate analysis showed that increased amount of alcohol intake was associated with high SWV. Conclusion: The SWV of the pancreas was measured with excellent success rate. However, tendency of higher SWV obtained from the pancreas harboring pancreatic cancer needed to be further investigated.

  18. Model based feasibility study on bidirectional check valves in wave energy converters

    DEFF Research Database (Denmark)

    Hansen, Anders Hedegaard; Pedersen, Henrik C.; Andersen, Torben Ole

    2014-01-01

    Discrete fluid power force systems have been proposed as the primary stage for Wave Energy Converters (WEC’s) when converting ocean waves into electricity, this to improve the overall efficiency of wave energy devices. This paper presents a model based feasibility study of using bidirectional check...

  19. Results of an Experimental Study of the Langlee Wave Energy Converter

    DEFF Research Database (Denmark)

    Pecher, Arthur; Kofoed, Jens Peter; Espedal, J.

    2010-01-01

    This paper presents the results of the first experimental study of the Langlee wave energy converter (WEC), a semi-submerged oscillating wave surge converter. Its design extracts the energy from the surge motion of the waves through two pairs of working flaps, called water wings, which are placed...

  20. The Lukash Plane-Wave Attractor and Relative Energy

    CERN Document Server

    Korunur, M; Salti, M; Aydogdu, Oktay; Korunur, Murat; Salti, Mustafa

    2006-01-01

    We study energy distribution in the context of teleparallel theory of gravity, due to matter and fields including gravitation, of the universe based on the plane-wave Bianchi VII$_{\\delta}$ spacetimes described by the Lukash metric. In order to make this calculation we consider the teleparallel gravity analogs of the energy-momentum formulations of Einstein, Bergmann-Thomson and Landau-Lifshitz. We find that Einstein and Bergmann-Thomson prescriptions agree with each other and give the same results for the energy distribution in a given spacetime, but the Landau-Lifshitz complex does not. Energy density turns out to be non-vanishing in all of these prescriptions. It is interesting to mention that the results can be reduced to the already available results for the Milne universe when we write $\\omega=1$ and $\\Xi^2=1$ in the metric of the Lukash spacetime, and for this special case, we get the same relation among the energy-momentum formulations of Einstein, Bergmann-Thomson and Landau-Lifshitz as obtained for ...

  1. Cosmology with space-based gravitational-wave detectors --- dark energy and primordial gravitational waves ---

    CERN Document Server

    Nishizawa, Atsushi; Taruya, Atsushi; Tanaka, Takahiro

    2011-01-01

    Proposed space-based gravitational-wave (GW) detectors such as DECIGO and BBO will detect ~10^6 neutron-star (NS) binaries and determine the luminosity distances to the binaries with high precision. Combining the luminosity distances with cosmologically-induced phase corrections on the GWs, cosmological expansion out to high redshift can be measured without the redshift determinations of host galaxies by electromagnetic observation and be a unique probe for dark energy. On the other hand, such a NS-binary foreground should be subtracted to detect primordial GWs produced during inflation. Thus, the constraining power on dark energy and the detectability of the primordial gravitational waves strongly depend on the detector sensitivity and are in close relation with one another. In this paper, we investigate the constraints on the equation of state of dark energy with future space-based GW detectors with/without identifying the redshifts of host galaxies. We also study the sensitivity to the primordial GWs, prop...

  2. Initial Assessment of Mooring Solutions for Floating Wave Energy Converters

    DEFF Research Database (Denmark)

    Thomsen, Jonas Bjerg; Kofoed, Jens Peter; Delaney, Martin

    2016-01-01

    The present study investigates three different types of mooring systems in order to establish potential cost reductions and applicability to wave energy converters (WECs). Proposed mooring systems for three existing WECs create the basis for this study, and the study highlights areas of interest ...... type system can provide a paramount cost reduction compared to a traditional CALM type system with chain lines. Similarly, use of nylon ropes similarly appears to provide low cost.......The present study investigates three different types of mooring systems in order to establish potential cost reductions and applicability to wave energy converters (WECs). Proposed mooring systems for three existing WECs create the basis for this study, and the study highlights areas of interest...... using a preliminary cost estimation and discussion of buildability issues. Using synthetic rope and variations in the mooring configuration has the potential of influencing the cost significantly. In order to quantify this potential, a simple quasi-static analysis is performed, which shows that a SALM...

  3. Evaluation of Various Technologies for Wave Energy Conversion in the Portuguese Nearshore

    Directory of Open Access Journals (Sweden)

    Carlos Guedes Soares

    2013-03-01

    Full Text Available The objective of the present work is to perform an evaluation of the performance provided by various technologies for wave energy conversion in the Portuguese continental coastal environment. The wave climate in the target area is first analyzed using the results from three years of simulations with a wave prediction system based on numerical models. Based on the above data, diagrams for the bivariate distributions of the sea states occurrences, defined by the significant wave height and the energy period, are designed for both winters and whole years. On this basis, the output of five different technologies for the conversion of wave energy is assessed in some relevant locations from the Portuguese nearshore. According to the results obtained, the Portuguese continental coastal environment appears to be appropriate for the wave energy extraction. At the same time, the present work shows that the output of the wave energy conversion devices does not depend only on the average wave energy but is also dependent on the distribution of the wave energy among the sea states of different periods. For this reason, a good agreement between the characteristics of the power matrices of the wave energy converters operating in a certain place and the diagrams for the bivariate distributions of the sea states occurrences corresponding to the considered location represents a key issue in selecting the most appropriate technology for wave energy conversion.

  4. Rossby wave energy dispersion from tropical cyclone in zonal basic flows

    Science.gov (United States)

    Shi, Wenli; Fei, Jianfang; Huang, Xiaogang; Liu, Yudi; Ma, Zhanhong; Yang, Lu

    2016-04-01

    This study investigates tropical cyclone energy dispersion under horizontally sheared flows using a nonlinear barotropic model. In addition to common patterns, unusual features of Rossby wave trains are also found in flows with constant vorticity and vorticity gradients. In terms of the direction of the energy dispersion, the wave train can rotate clockwise and elongate southwestward under anticyclonic circulation (ASH), which contributes to the reenhancement of the tropical cyclone (TC). The wave train even splits into two obvious wavelike trains in flows with a southward vorticity gradient (WSH). Energy dispersed from TCs varies over time, and variations in the intensity of the wave train components typically occur in two stages. Wave-activity flux diagnosis and ray tracing calculations are extended to the frame that moves along with the TC to reveal the concrete progress of wave propagation. The direction of the wave-activity flux is primarily determined by the combination of the basic flow and the TC velocity. Along the flux, the distribution of pseudomomentum effectively illustrates the development of wave trains, particularly the rotation and split of wave propagation. Ray tracing involves the quantitative tracing of wave features along rays, which effectively coincide with the wave train regimes. Flows of a constant shear (parabolic meridional variation) produce linear (nonlinear) wave number variations. For the split wave trains, the real and complex wave number waves move along divergent trajectories and are responsible for different energy dispersion ducts.

  5. Analysis of Wave Reflection from Wave Energy Converters Installed as Breakwaters in Harbour

    DEFF Research Database (Denmark)

    Zanuttigh, B.; Margheritini, Lucia; Gambles, L.

    2009-01-01

    Amplification and renovation of harbours, none the last for the need of straitening existing structures because of the increased storminess due to climate change, is a practice that is repeating itself all around the world. To this purpose, integration of breakwaters and Wave Energy Converters...... (WECs) based on two different technologies, one based on the overtopping principle and the other of Oscillating Water Column (OWC) type, revealed to be suitable with different advantages compared to offshore installations, among the others: sharing of costs, cheaper accessibility and maintenance, lower...

  6. Evaluation of turbulent magnetic energy spectra in the three-dimensional wave vector domain in the solar wind

    Energy Technology Data Exchange (ETDEWEB)

    Gary, S Peter [Los Alamos National Laboratory; Narita, Y [UNIV OF BRAUNSCHWEIG; Glassmeier, K H [UNIV OF BRAUNSCHWEIG; Goldstein, M L [NGSFC; Safraoui, F [NGSFC; Treumann, R A [UNIV. MUNICH

    2009-01-01

    Using four-point measurements of the CLUSTER spacecraft, the energy distribution of magnetic field fluctuations in the solar wind is determined directly in the three-dimensional wave vector domain in the range 3 x 10{sup -4} rad/km < k < 3 x 10{sup -3} rad/km. The analysis method takes account of a regular tetrahedron configuration of CLUSTER and the Doppler effect. The energy distribution in the flow rest frame is anisotropic, characterized by two distinct extended structures perpendicular to the mean magnetic field and furthermore perpendicular to the flow direction. The three-dimensional distribution is averaged around the direction of the mean magnetic field direction, and then is further reduced to one-dimensional distributions in the wave number domain parallel and perpendicular to the mean magnetic field. The one-dimensional energy spectra are characterized by the power law with the index -5/3 and furthermore very close energy density between parallel and perpendicular directions to the mean magnetic field at the same wave numbers. Though the distributions and the spectra are not covered in a wide range of wave vectors, our measurements suggest that the solar wind fluctuation is anisotropic in the three-dimensional wave vector space. It is, however, rather isotropic when reduced into the parallel and perpendicular wave vector geometries due to the second anisotropy imposed by the flow direction.

  7. 75 FR 27999 - CenterPoint Energy Gas Transmission Company; Notice of Application

    Science.gov (United States)

    2010-05-19

    ... gas supplies can be redirected from Dunn Junction Compressor Station to the Dunn Compressor Station... Energy Regulatory Commission CenterPoint Energy Gas Transmission Company; Notice of Application May 12, 2010. Take notice that on May 11, 2010, CenterPoint Energy Gas Transmission Company (CEGT), 1111...

  8. Observation of Strong Reflection of Electron Waves Exiting a Ballistic Channel at Low Energy

    Science.gov (United States)

    Vaz, Canute I.; Liu, Changze; Campbell, Jason P.; Ryan, Jason T.; Southwick, Richard G.; Gundlach, David; Oates, Anthony S.; Huang, Ru; Cheung, Kin. P.

    2016-01-01

    Wave scattering by a potential step is a ubiquitous concept. Thus, it is surprising that theoretical treatments of ballistic transport in nanoscale devices, from quantum point contacts to ballistic transistors, assume no reflection even when the potential step is encountered upon exiting the device. Experiments so far seem to support this even if it is not clear why. Here we report clear evidence of coherent reflection when electron wave exits the channel of a nanoscale transistor and when the electron energy is low. The observed behavior is well described by a simple rectangular potential barrier model which the Schrodinger's equation can be solved exactly. We can explain why reflection is not observed in most situations but cannot be ignored in some important situations. Our experiment also represents a direct measurement of electron injection velocity - a critical quantity in nanoscale transistors that is widely considered not measurable. PMID:27882264

  9. Theoretical and Experimental Study on the Acoustic Wave Energy After the Nonlinear Interaction of Acoustic Waves in Aqueous Media

    Institute of Scientific and Technical Information of China (English)

    兰朝凤; 李凤臣; 陈欢; 卢迪; 杨德森; 张梦

    2015-01-01

    Based on the Burgers equation and Manley-Rowe equation, the derivation about nonlinear interaction of the acoustic waves has been done in this paper. After nonlinear interaction among the low-frequency weak waves and the pump wave, the analytical solutions of acoustic waves’ amplitude in the field are deduced. The relationship between normalized energy of high-frequency and the change of acoustic energy before and after the nonlinear interaction of the acoustic waves is analyzed. The experimental results about the changes of the acoustic energy are presented. The study shows that new frequencies are generated and the energies of the low-frequency are modulated in a long term by the pump waves, which leads the energies of the low-frequency acoustic waves to change in the pulse trend in the process of the nonlinear interaction of the acoustic waves. The increase and decrease of the energies of the low-frequency are observed under certain typical conditions, which lays a foundation for practical engineering applications.

  10. Energy and Information Transfer Via Coherent Exciton Wave Packets

    Science.gov (United States)

    Zang, Xiaoning

    Electronic excitons are bound electron-hole states that are generated when light interacts with matter. Such excitations typically entangle with phonons and rapidly decohere; the resulting electronic state dynamics become diffusive as a result. However, if the exciton-phonon coupling can be reduced, it may be possible to construct excitonic wave packets that offer a means of efficiently transmitting information and energy. This thesis is a combined theory/computation investigation to design condensed matter systems which support the requisite coherent transport. Under the idealizing assumption that exciton-phonon entanglement could be completely suppressed, the majority of this thesis focuses on the creation and manipulation of exciton wave packets in quasi-one-dimensional systems. While each site could be a silicon quantum dot, the actual implementation focused on organic molecular assemblies for the sake of computational simplicity, ease of experimental implementation, potential for coherent transport, and promise because of reduced structural uncertainty. A laser design was derived to create exciton wave packets with tunable shape and speed. Quantum interference was then exploited to manipulate these packets to block, pass, and even dissociate excitons based on their energies. These developments allow exciton packets to be considered within the arena of quantum information science. The concept of controllable excitonic wave packets was subsequently extended to consider molecular designs that allow photons with orbital angular momentum to be absorbed to create excitons with a quasi-angular momentum of their own. It was shown that a well-defined measure of topological charge is conserved in such light-matter interactions. Significantly, it was also discovered that such molecules allow photon angular momenta to be combined and later emitted. This amounts to a new way of up/down converting photonic angular momentum without relying on nonlinear optical materials. The

  11. Wave-to-wire Modelling of Wave Energy Converters : Critical Assessment, Developments and Applicability for Economical Optimisation

    DEFF Research Database (Denmark)

    Ferri, Francesco

    untapped, renewable energy resource that has the potential to contribute significantly to the future energy mix, especially in an environmental friendly future scenario. What is bounding the sector to roll off into the market is the cost of the produced energy: too high if compared with other renewable......The idea to use the motion of a wavy sea surface to produce electricity was investigate in the seventies, in a time when the earliest wave energy converters were conceived and developed. But nowadays still none of the patented devices reached a commercial stage. Wave energy is a large, mostly...

  12. RESEARCH FOR THE STRAIN ENERGY RELEASE RATE OF COMPLEX CRACKS BY USING POINT-BY-POINT CLOSED EXTRAPOLATION APPROACH

    Institute of Scientific and Technical Information of China (English)

    郭茂林; 孟庆元; 王彪

    2003-01-01

    A new extrapolation approach was proposed to calculate the strain energy release rates of complex cracks. The point-by-point closed method was used to calculate the closed energy, thus the disadvantage of self inconsistency in some published papers can be avoided. The disadvantage is that the closed energy is repeatedly calculated: when closed nodal number along radial direction is more than two, the displacement of nodes behind the crack tip that is multiplied by nodal forces, the closed energy has been calculated and the crack surfaces have been closed, and that closed energy of middle point is calculated repeatedly. A DCB ( double cantilever beam) specimen was calculated and compared with other theoretical results, it is shown that a better coincidence is obtained. In addition the same results are also obtained for compact tension specimen, three point bend specimen and single edge cracked specinen. In comparison with theoretical results, the error can be limited within 1 per cent. This method can be extended to analyze the fracture of composite laminates with various delamination cracks.

  13. Strategy for the development of wave energy utilization in Denmark through an industrial partnership

    DEFF Research Database (Denmark)

    2013-01-01

    The Danish wave energy sector has during 2011-12 carried out a project called ‘A new strategy for wave energy through industrial partnership’ described in the document ‘Wave Energy Technology, Strategy for Research, Development and Demonstration 2012’ [1]. The project was funded by the Danish...... energy. This paper will present the development plan described by the partnership in order to realize their vision, including the collaborative focus areas for technological development, the timeframe and the required support structure identified by the Danish Partnership for Wave Energy....

  14. Optimization of sources for focusing wave energy in targeted formations

    KAUST Repository

    Jeong, C

    2010-06-08

    We discuss a numerical approach for identifying the surface excitation that is necessary to maximize the response of a targeted subsurface formation. The motivation stems from observations in the aftermath of earthquakes, and from limited field experiments, whereby increased oil production rates were recorded and were solely attributable to the induced reservoir shaking. The observations suggest that focusing wave energy to the reservoir could serve as an effective low-cost enhanced oil recovery method. In this paper, we report on a general method that allows the determination of the source excitation, when provided with a desired maximization outcome at the targeted formation. We discuss, for example, how to construct the excitation that will maximize the kinetic energy in the target zone, while keeping silent the neighbouring zones. To this end, we cast the problem as an inverse-source problem, and use a partial-differential- equation-constrained optimization approach to arrive at an optimized source signal. We seek to satisfy stationarity of an augmented functional, which formally leads to a triplet of state, adjoint and control problems. We use finite elements to resolve the state and adjoint problems, and an iterative scheme to satisfy the control problem to converge to the sought source signal. We report on one-dimensional numerical experiments in the time domain involving a layered medium of semi-infinite extent. The numerical results show that the targeted formation\\'s kinetic energy resulting from an optimized wave source could be several times greater than the one resulting from a blind source choice, and could overcome the mobility threshold of entrapped reservoir oil. © 2010 Nanjing Geophysical Research Institute.

  15. Irregular Wave Energy Extraction Analysis for a Slider Crank WEC Power Take-Off System

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Yuanrui; Karayaka, H. Bora; Yan, Yanjun; Zhang, James Z.; Muljadi, Eduard

    2015-09-02

    Slider crank Wave Energy Converter (WEC) is a novel energy conversion device. It converts wave energy into electricity at a relatively high efficiency, and it features a simple structure. Past analysis on this WEC has been done under regular sinusoidal wave conditions, and a suboptimal energy could be achieved. This paper presents the analysis of the system under irregular wave conditions; a time-domain hydrodynamics model is adopted and the control methodology is modified to better serve the irregular wave conditions. Results from the simulations show that the performance of the system under irregular wave conditions is different from that under regular sinusoidal wave conditions, but still a reasonable amount of energy can be extracted.

  16. Fast Magnetoacoustic Waves in a Fan Structure Above a Coronal Magnetic Null Point

    Science.gov (United States)

    Mészárosová, H.; Dudík, J.; Karlický, M.; Madsen, F. R. H.; Sawant, H. S.

    2013-04-01

    We analyze the 26 November 2005 solar radio event observed interferometrically at frequencies of 244 and 611 MHz by the Giant Metrewave Radio Telescope (GMRT) in Pune, India. These observations are used to make interferometric maps of the event at both frequencies with the time cadence of 1 s from 06:50 to 07:12 UT. These maps reveal several radio sources. The light curves of these sources show that only two sources at 244 MHz and 611 MHz are well correlated in time. The EUV flare is more localized with flare loops located rather away from the radio sources. Using SoHO/MDI observations and potential magnetic field extrapolation we demonstrate that both the correlated sources are located in the fan structure of magnetic field lines starting from a coronal magnetic null point. Wavelet analysis of the light curves of the radio sources detects tadpoles with periods in the range P=10 - 83 s. These wavelet tadpoles indicate the presence of fast magnetoacoustic waves that propagate in the fan structure of the coronal magnetic null point. We estimate the plasma parameters in the studied radio sources and find them consistent with the presented scenario involving the coronal magnetic null point.

  17. Physical Modelling of an Array of 25 Heaving Wave Energy Converters to Quantify Variation of Response and Wave Conditions

    DEFF Research Database (Denmark)

    2013-01-01

    for the evaluation of array interaction models and environmental scale models. Each wave energy converter unit has a diameter of 0.315 m and power absorption is due to friction of both a power take off system and bearings. Response is measured on all floats and surge force on five floats. Wave gauges are located...

  18. Sea ice floes dissipate the energy of steep ocean waves

    CERN Document Server

    Toffoli, Alessandro; Meylan, Michael H; Cavaliere, Claudio; Alberello, Alberto; Elsnab, John; Monty, Jason P

    2015-01-01

    Wave attenuation by ice floes is an important parameter for modelling the Arctic Oceans. At present, attenuation coefficients are extracted from linear models as a function of the incident wave period and floe thickness. Recent explorations in the Antarctic Mixed Ice Zone (MIZ) revealed a further dependence on wave amplitude, suggesting that nonlinear contributions are non-negligible. An experimental model for wave attenuation by a single ice floe in a wave flume is here presented. Observations are compared with linear predictions based on wave scattering. Results indicate that linear models perform well under the effect of gently sloping waves. For more energetic wave fields, however, transmitted wave height is normally over predicted. Deviations from linearity appear to be related to an enhancement of wave dissipation induced by unaccounted wave-ice interaction processes, including the floe over wash.

  19. Single-wave-number representation of nonlinear energy spectrum in elastic-wave turbulence of the Föppl-von Kármán equation: energy decomposition analysis and energy budget.

    Science.gov (United States)

    Yokoyama, Naoto; Takaoka, Masanori

    2014-12-01

    A single-wave-number representation of a nonlinear energy spectrum, i.e., a stretching-energy spectrum, is found in elastic-wave turbulence governed by the Föppl-von Kármán (FvK) equation. The representation enables energy decomposition analysis in the wave-number space and analytical expressions of detailed energy budgets in the nonlinear interactions. We numerically solved the FvK equation and observed the following facts. Kinetic energy and bending energy are comparable with each other at large wave numbers as the weak turbulence theory suggests. On the other hand, stretching energy is larger than the bending energy at small wave numbers, i.e., the nonlinearity is relatively strong. The strong correlation between a mode a(k) and its companion mode a(-k) is observed at the small wave numbers. The energy is input into the wave field through stretching-energy transfer at the small wave numbers, and dissipated through the quartic part of kinetic-energy transfer at the large wave numbers. Total-energy flux consistent with energy conservation is calculated directly by using the analytical expression of the total-energy transfer, and the forward energy cascade is observed clearly.

  20. Point-source and diffuse high-energy neutrino emission from Type IIn supernovae

    Science.gov (United States)

    Petropoulou, M.; Coenders, S.; Vasilopoulos, G.; Kamble, A.; Sironi, L.

    2017-09-01

    Type IIn supernovae (SNe), a rare subclass of core collapse SNe, explode in dense circumstellar media that have been modified by the SNe progenitors at their last evolutionary stages. The interaction of the freely expanding SN ejecta with the circumstellar medium gives rise to a shock wave propagating in the dense SN environment, which may accelerate protons to multi-PeV energies. Inelastic proton-proton collisions between the shock-accelerated protons and those of the circumstellar medium lead to multimessenger signatures. Here, we evaluate the possible neutrino signal of Type IIn SNe and compare with IceCube observations. We employ a Monte Carlo method for the calculation of the diffuse neutrino emission from the SN IIn class to account for the spread in their properties. The cumulative neutrino emission is found to be ∼10 per cent of the observed IceCube neutrino flux above 60 TeV. Type IIn SNe would be the dominant component of the diffuse astrophysical flux, only if 4 per cent of all core collapse SNe were of this type and 20-30 per cent of the shock energy was channeled to accelerated protons. Lower values of the acceleration efficiency are accessible by the observation of a single Type IIn SN as a neutrino point source with IceCube using up-going muon neutrinos. Such an identification is possible in the first year following the SN shock breakout for sources within 20 Mpc.